Magnetic Effects Of Electric Current - Class 10 Physics - Extra Questions
It is established that an electric current through a metallic conductor produces a magnetic field around it. Is there a similarmagnetic field produced around a thin beam of moving (i) positivelycharged alpha particles, (ii) neutrons? Justify your answer by giving suitable arguments.
Write two properties of magnetic field lines.
An electric generator works on the principle of ________ .
An electric generator works on the principle of Faraday's laws of electromagnetic induction,.i.e. when a conductor moves in a magnetic field, the flux linked to it changes and hence an e.m.f is induced in that conductor and current is produced.
Working:- When the conductor loop attached on the iron core rotates inside the magnetic field, emf is induced across its arm and hence current is generated, as the flux linked with the loop changes sinusoidally.
Are the magnetic lines of force always parallel to a straight conductor carrying an electric current? Explain.
The magnetic lines of force are always perpendicular to a straight conductor carrying an electric current.
The Right-hand Thumb rule is used to identify the directions of the magnetic lines of force and electric current.
It states that when an electric current passes through a straight wire that is held by the right hand with the thumb pointing upwards and the fingers curling up the wire, the thumb points in the direction of the conventional current (from positive to negative), and the fingers point in the direction of the magnetic field.
The Right-hand Thumb rule is used to identify the directions of the magnetic lines of force and electric current.
It states that when an electric current passes through a straight wire that is held by the right hand with the thumb pointing upwards and the fingers curling up the wire, the thumb points in the direction of the conventional current (from positive to negative), and the fingers point in the direction of the magnetic field.
So, the given statement is false.
A straight wire lying in a horizontal plane carries a current from magnetic north to magnetic south. What is the direction of force felt by the wire?
State whether true or false :The magnetic field lines originate from the south pole and terminate at the north pole of the magnet.
Clearly as shown in the figure, the magnetic lines of force originate from north pole outside the magnet and terminate at the south pole.
What is a magnet?
Name some devices in which electric motors are used.
Magnetic lines of force around any current carrying conductor are circular in nature.
Fill in the blanks.
The device that detects the induced emf is called ____________.
What is the purpose of using a fuse in an electrical circuit?
State whether true or false :Electro magnetic induction is a phenomenon of production of electric current in a coil, when the magnetic flux linked with the coil is changed.
What are the characteristic properties of fuse wire?
What is consumed by different electrical appliances, for which electricity bills are paid?
How should the electric lamps in a building be connected?
Write few measures to minimize electricity consumption at home.
At what voltage is the alternating current supplied to our houses?
When is the displacement of the conductor maximum, if the conductor is placed in the magnetic field?
Define Flemings left hand Rule.
Define electromagnetic induction?
What is the direction of the force acting on a charged particle $$q$$ ,moving with velocity $$V$$ in a uniform magnetic field?
Greater the current in the wire _______ will be the magnetic field produced.
State the observations made by Oerested on the basis of his experiments with current carrying conductor.
What is the major difference between the simple alternator and most practical alternators?
A rectangular coil ABCD having a battery connected between its ends A and D is placed in between the pole pieces of a horseshoe magnet as shown in Fig . 10.26.
(i) What is the direction of current in the coil?
(ii) What is the direction of force on each arm?
(iii) What is the effect of the forces on coil?
(iv) How is the effect of forces on coil changed if the connections at the terminals of battery are interchanged?
$$\large\textbf{Part(a): Direction of Electric current}$$
Electric current always flows from battery positive terminal to negative terminal (High potential to low potential.)
In Fig. the current in coil is in direction $$DCBA.$$
$$\large\textbf{Part(b): Direction of Force}$$
Direction of force on Each arm can be predicted by Fleming’s left hand rule.
$$Fleming's$$ $$left$$ $$hand$$ $$rule:$$ It states that if we stretch our left hand fingers such that the forefinger, second finger and thumb perpendicular to each other. If the forefinger represents the direction of the field and the second finger represents that of the current, then the thumb gives the direction of the force.”
$$\bullet$$The magnitude of the force is given by the fomula:
Force, $$F$$ $$=$$$$IlbSin{\theta}$$
here $$\theta$$ is the angle between magnetic field and length of conductor, $$l$$ is the length of the wire.
$$\bullet$$ For the arm AB, $$\theta = 90 degree$$, by the Fleming left hand rule, the force is outward at right angles to the plane of coil.
$$\bullet$$ For the arm CD, $$\theta = 90 degree$$, by the Fleming left hand rule, the force is inward perpendicular to the plane of coil.
$$\bullet$$ On the arm BC and AD, no froce act on them as they are parallel to magnetic filed.
hence, $$\theta = 0$$
$$F = ILB Sin (0) = Zero$$
$$\large\textbf{Part(C): Turning effect of Force}$$
The force on the arms AB and CD are equal in magnitude, but opposite in direction. They form a clockwise couple. So the coil will rotate clockwise with the arm AB coming out and the arm CD going in.
$$\large\textbf{Part(D): Effect of Force, on exchanging Polarity of terminals}$$
On interchanging the terminals of battery, the direction of current in coil is reversed, hence direction of force as well as direction of rotation of the coil reverses.
Coil will rotate in counterclockwise manner.
The three diagrams in the following figure shows the lines of force ( field lines) between the poles of two magnets. Identify the poles $$A, B, C, D, E$$ and $$F$$.
What is the other name of Maxwell's right-hand thumb rule?
What do you mean by magnetic field ?
Fleming's Rule for the motor effect uses the........... hand
State the colour coding of the three wires in a cable .
Write one application of the following:
Fleming's Left-Hand Rule
What is the color code for insulation on the (a) live (b) neutral and (c) earth wire?
Name four appliances which work using electricity.
What does the divergence of magnetic field lines near the ends of a current carrying straight solenoid indicate?
Draw a labelled circuit diagram of a simple electric motor and explain its working. In what way these simple electric motors are different from commercial motors?
Principle of a simple electric motor is when a rectangular coil carrying current is placed in a magnetic field, a torque acts on the coil which rotates it continuously. When the coil rotates, the shaft attached to it also rotates and thus it is able to do mechanical work. The main parts of electric motor are the magnets, armature, split ring commutators and brushes. The armature consists of a rectangular coil made of insulated copper wire wound on a soft iron core. The coil is mounted on an axle and is placed between the cylindrical concave poles of a magnet. The commutator is used to reverse the direction of flow of current. It is a copper ring split into two parts P and Q. The split rings are insulated from each other and mounted on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate along with the coil. Commutator rings are connected to a battery. The wires from the battery are not connected to the rings but to the brushes which are in contact with the rings. The brushes are two small strips of carbon, which press slightly against the two split rings, and the split rings rotate between the brushes. The carbon brushes are connected to a D.C. source.
Working of the Electric motor:
When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn towards the right, causing rotation. When the coil turns through 90 degrees, the brushes lose contact with the commutator and the current stops flowing through the coil. However, the coil keeps turning because of its own momentum. Now when the coil turns through 180 degrees, the sides get interchanged. As a result the commutator ring P is now in contact with brush Y and commutator ring Q is in contact with brush X. Therefore, the current continues to flow in the same direction.
Difference between simple electric motors and commercial electric motors:
In commercial electric motors, field coils are used for producing magnetic fields and not a permanent magnet as in simple electric motors. These coils become magnetized when current is passed through them. Field coils give a stronger, more easily shaped magnetic field than permanent magnets. More the number of turns in the field coil, more the magnetic field. Therefore, the suitable field coil sizes are used for various commercial purposes.
Working of the Electric motor:
When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn towards the right, causing rotation. When the coil turns through 90 degrees, the brushes lose contact with the commutator and the current stops flowing through the coil. However, the coil keeps turning because of its own momentum. Now when the coil turns through 180 degrees, the sides get interchanged. As a result the commutator ring P is now in contact with brush Y and commutator ring Q is in contact with brush X. Therefore, the current continues to flow in the same direction.
Difference between simple electric motors and commercial electric motors:
In commercial electric motors, field coils are used for producing magnetic fields and not a permanent magnet as in simple electric motors. These coils become magnetized when current is passed through them. Field coils give a stronger, more easily shaped magnetic field than permanent magnets. More the number of turns in the field coil, more the magnetic field. Therefore, the suitable field coil sizes are used for various commercial purposes.
What is the role of the two conducting stationary brushes in a simple electric motor?
The torque on a electric motor is kept from reversing every time the coil moves through the plane perpendicular to the magnetic field, by a split-ring device called a commutator that is used to reverse the current at that point. The electrical supplies to the outer side of the rotating split-ring commutator are done using Brushes. The current in the coil of the electric motor is supplied through the two brushes that make moving contact with the commutator.
Name four appliances wherein an electric motor, a rotating device that converts electrical energy to mechanical energy, is used as an important component. In what respect motors are different from generators?
Meena draws magnetic field lines of the field close to the axis of a current-carrying circular loop. As she moves away from the centre of the circular loop she observes that the lines keep on diverging. How will you explain her observation :
Electric current in a circular loop creates a magnetic field which is more concentrated in the center of the loop than outside the loop.
Concentric circles are formed, which are centered at the point where the wire passes through the cardboard. The lines near the center of the loop are almost straight. The magnetic field at the centre of the loop is perpendicular to the plane of the loop. The concentric circles become larger as we move away from the wire because as the distance increases from the current carrying conductor the strength of the magnetic field fades away.
Thus, the strength of the magnetic field is inversely proportional to the distance from the current carrying conductor. That is, as the distance increases the magnetic field decreases. Hence, Meena observes that the lines keep diverging as she moves away from the circular loop.
Concentric circles are formed, which are centered at the point where the wire passes through the cardboard. The lines near the center of the loop are almost straight. The magnetic field at the centre of the loop is perpendicular to the plane of the loop. The concentric circles become larger as we move away from the wire because as the distance increases from the current carrying conductor the strength of the magnetic field fades away.
Thus, the strength of the magnetic field is inversely proportional to the distance from the current carrying conductor. That is, as the distance increases the magnetic field decreases. Hence, Meena observes that the lines keep diverging as she moves away from the circular loop.
Under what conditions permanent electromagnet is obtained if a current carrying solenoid is used? Support your answer with the help of a labelled circuit diagram.
A solenoid is a simple electromagnetic device consisting of a coiled electric wire, wrapped in a 3D circular pattern. When electric current is passed through the wire, the solenoid acts like a magnet with N and S poles at the ends of the coil.
When a ferromagnetic material rod is permanently placed inside the solenoid, the metal greatly increases the magnetic effect and becomes a permanent electromagnet. Moreover, it can also be used as an electrical switch by drawing in or pushing out a ferromagnetic material like an iron rod. Depending on the directions of the rod and the electrical current the switching action takes place.
Given figure represents the solenoid as electromagnet and the switching action.
When a ferromagnetic material rod is permanently placed inside the solenoid, the metal greatly increases the magnetic effect and becomes a permanent electromagnet. Moreover, it can also be used as an electrical switch by drawing in or pushing out a ferromagnetic material like an iron rod. Depending on the directions of the rod and the electrical current the switching action takes place.
Given figure represents the solenoid as electromagnet and the switching action.
A solenoid is a coil of insulated or enameled wire wound on a rod-shaped form made of solid iron, solid steel, or powdered iron.
State whether this statement is true or false.Write 1 for True and 2 for False
Describe an activity to draw the magnetic field is produced around a current carrying conductor
The pattern of magnetic field lines around a straight conductor carrying current can be described by the following activity.
(i) Insert vertically a long straight wire carrying an electric current so that it passes through the centre of a horizontal piece of plastic board as shown in figure.
(ii) Take care that the plastic board is fixed and does not move up and down. Now, sprinkle some iron filings onto the plastic board to show the shape of the field.
(iii) You will notice that the iron filings get arranged around the wires in the shape of circles. This is due to the reason that the magnetic field lines around the current carrying straight conductor are circular. The iron filings align along these field lines.
(iv) On reversing the direction of flow of current, we observe that the iron filings arrange themselves in circles around the wire showing that the magnetic field lines are still circular in nature The direction of the magnetic field can be obtained by using a compass. If the current direction is reversed, the direction of the magnetic field is also reversed.
(a)When current through the wire is decreased, field also gets reduced.
(b) When the current is reversed, the field also gets reversed in direction.
Describe an activity to draw a magnetic field line outside a bar magnet from one pole to another.
The armature in a motor rotates due to the presence of a _______ field.
In our houses, we receive AC current at a voltage of ________ with a frequency of __________.
An AC generator can be converted into DC generator by replacing ................. .
An $$AC$$ generator can be converted into a $$DC$$ generator by replacing the slip rings of an $$AC$$ generator with the commutator of $$DC$$ generator,
Working; The only difference between $$AC$$ and $$DC$$ current is that in case of $$AC$$ the current Alternates the direction in the loop but in the case of $$DC$$ the current always flows in the same direction.
Generating slip ring is fixed with one side arm of the loop hence after $$ { 180 }^{ 0 }$$ turn of the loop the end becomes opposite polar than the previously charged. So the current flows in the opposite direction.
But in the case of the commutator which is just softly attached to the brushes they are exchanged with each other after every $${ 180 }^{ 0 }$$ turn.So although one end changes it's terminal yet it gets attached with other brush. Hence net effect is cancelled out and current follows the original direction.
The diagram shows a spiral coil wound on a hollow cardboard tube AB. A magnetic compass is placed close to it. Current is switched on by closing the key. How will the compass needle be affected? Give reason.
The polarity of the magnetic field (that is, which end is magnetic-north or magnetic-south) can easily be found from the Right hand thumb rule. If we hold the solenoid in our right hand, so that the fingers curl around it in the direction of the conventional current flow, then the thumb will point to the north pole of the magnet. Also, a solenoid when suspended freely, aligns itself in the north-south direction, thus behaving like a bar magnet. One end of the solenoid acts like a north pole and the other end the south pole.
The polarity of the solenoid AB can be changed by reversing the direction of the current. If we imagine that we are facing the coil end-on, then if the current flows in a clockwise direction, we are looking at the south pole. If the current flows in an anticlockwise direction, we are looking at the north pole. Hence, the polarity at A is north and polarity at B is south.
When magnetic compass with the north end is brought closer to the A end of the solenoid AB, the needle deflects towards the west, that is away from the solenoid because the magnetic compass that is pointing in the direction of the earth's magnetic field, i.e. north- south direction repels with the north pole of current carrying solenoid. Like poles repel each other.
This is the fundamental principle of magnetism.
What will happen to a compass needle when the compass is placed below a wire and a current is made to flow through the wire? Give a reason to justify your answer.
Name and state the rule by which polarity at the ends of a current carrying solenoid is determined.
The magnetic fields produced by the solenoid are similar to the magnetic field produced by a bar magnet. The polarity of the magnetic field (that is, which end is magnetic-north or magnetic-south) can be found from the Right hand thumb rule. If we hold the solenoid in our right hand, so that the fingers curl around it in the direction of the conventional current flow, then the thumb will point to the north pole of the magnet.
Note: The polarity of a solenoid can be reversed by reversing the direction of the current.
Note: The polarity of a solenoid can be reversed by reversing the direction of the current.
Describe one experiment to demonstrate the phenomenon of electromagnetic induction.
Definition:
Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field.
Experiment:
Two different coils of copper wire having large number of turns (say 50 and 100 turns respectively) are taken. They are now inserted over a non-conducting cylindrical roll, as shown in figure below.
The coil-1, having larger number of turns, is connected in series with a battery and a plug key. Also, the other coil-2 is connected with a galvanometer as shown.
The key is initiated and the galvanometer is observed. We will observe that the needle of the galvanometer instantly jumps to one side and then quickly returns to zero, indicating a momentary current in coil-2.
The coil-1 is now disconnected from the battery. Now we will observe that the needle momentarily moves, but to the opposite side. It means that now the current flows in the opposite direction in coil-2.
Observations:
From these observations, we conclude that a potential difference is induced in the coil-2 whenever the electric current through the coil 1 is changing (starting or stopping). As the current in the first coil changes, the magnetic field associated with it also changes. Thus the magnetic field lines around the secondary coil also change. Hence the change in magnetic field lines associated with the secondary coil is the cause of induced electric current in it. This process, by which a changing magnetic field in a conductor induces a current in
another conductor, is called electromagnetic induction.
In practice, we can induce current in a coil either by moving it in a magnetic field or by changing the magnetic field around it. It is convenient in most situations to move the coil in a magnetic field.
How would you demonstrate that a momentary current can be obtained by the suitable use of a magnet, a coil of wire and galvanometer ?
When a magnet is moved closer to the current-carrying coil it will generate electricity as the coil moves through the magnetic field. As the magnet is moved, there will be an induced electro-motive force (EMF) which will produce a current in the coil. Once the magnet stops moving, the current will become zero.
Hence, when a galvanometer is connected to the circuit, there will be deflection due to the flow of electricity. As the magnet is moved toward the coil of wire, the needle of the galvanometer moves in one direction. As the magnet is moved away from the coil of wire, the needle of the galvanometer moves in the opposite direction. If the magnet is moved faster, the magnitude of the deflection increases.
If we hold the magnet in place and move the coil of the wire toward the magnet, the same thing happens. The magnitude of the induced current and voltage is dependent on the relative motion of the coil of wire and the magnet. The mechanical movement is converted into electrical energy.
You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch. Draw a circuit diagram to represent the process.
An electromagnet is a coil of current-carrying wire wound around an iron core as shown in the attached figure. When connected to a current source, the electromagnet becomes energised, creating a magnetic field just like a permanent magnet. The polarity of an electromagnet can be determined using right-hand thumb rule.
Complete the diagram with commutator, etc. for the flow of current in the coil.
The rectangular coil ABCD is placed in between the magnetic field and when current flows through the coil from the split ring commutator, a torque acts on the coil which rotates it continuously. To keep the torque from reversing every time the coil moves through the plane perpendicular to the magnetic field according to Fleming's right hand thumb rule, the split ring device is used to reverse the current at that point and maintain the direction of the current in the external circuit to flow in the same direction as DC current.
The diagram is given below.
The diagram is given below.
What is electromagnetic induction?
What is an electric motor ? State its principle.
Almost every mechanical movement that we see around us is accomplished by an electric motor. Electric machines are a means of converting energy. Motors take electrical energy and produce mechanical energy. Electric motors are used to power hundreds of devices we use in everyday life. The input is electrical energy (from the supply source), and the output is mechanical energy (to the load).
Electrical energy is converted into mechanical energy by a d.c. motor.
Principle of a simple electric motor:
When a rectangular coil carrying current is placed in a magnetic field, a torque acts on the coil which rotates it continuously. When the coil rotates, the shaft attached to it also rotates and thus it is able to do mechanical work. The main parts of electric motor are the magnets, armature, split ring commutators and brushes. The armature consists of a rectangular coil made of insulated copper wire wound on a soft iron core. The coil is mounted on an axle and is placed between the cylindrical concave poles of a magnet. The commutator is used to reverse the direction of flow of current. It is a copper ring split into two parts P and Q. The split rings are insulated from each other and mounted on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate along with the coil. Commutator rings are connected to a battery. The wires from the battery are not connected to the rings but to the brushes which are in contact with the rings. The brushes are two small strips of carbon, which press slightly against the two split rings, and the split rings rotate between the brushes. The carbon brushes are connected to a D.C. source.
Electrical energy is converted into mechanical energy by a d.c. motor.
Principle of a simple electric motor:
When a rectangular coil carrying current is placed in a magnetic field, a torque acts on the coil which rotates it continuously. When the coil rotates, the shaft attached to it also rotates and thus it is able to do mechanical work. The main parts of electric motor are the magnets, armature, split ring commutators and brushes. The armature consists of a rectangular coil made of insulated copper wire wound on a soft iron core. The coil is mounted on an axle and is placed between the cylindrical concave poles of a magnet. The commutator is used to reverse the direction of flow of current. It is a copper ring split into two parts P and Q. The split rings are insulated from each other and mounted on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate along with the coil. Commutator rings are connected to a battery. The wires from the battery are not connected to the rings but to the brushes which are in contact with the rings. The brushes are two small strips of carbon, which press slightly against the two split rings, and the split rings rotate between the brushes. The carbon brushes are connected to a D.C. source.
Name and state the rule which is used to determine the direction of force on a current carrying conductor placed in a magnetic field.
The Fleming's left-hand rule gives the direction of force experienced by current carrying conductor placed in an external magnetic field.
Fleming's left hand rule:
When an electric current passes through a straight wire, an external magnetic field is applied across that flow, the wire experiences a force perpendicular both to the field and to the direction of the current flow. The Fleming's left hand rule can be used to determine the direction of the force, magnetic field and current. A left hand can be held, so that the thumb, first finger and second finger are held mutually perpendicular to each other. The thumb represents the direction of Motion resulting from the force on the conductor. The first finger represents the direction of the magnetic Field. The second finger represents the direction of the Current.
Fleming's left hand rule:
When an electric current passes through a straight wire, an external magnetic field is applied across that flow, the wire experiences a force perpendicular both to the field and to the direction of the current flow. The Fleming's left hand rule can be used to determine the direction of the force, magnetic field and current. A left hand can be held, so that the thumb, first finger and second finger are held mutually perpendicular to each other. The thumb represents the direction of Motion resulting from the force on the conductor. The first finger represents the direction of the magnetic Field. The second finger represents the direction of the Current.
An electric current has three effects heating, chemical and .......... .
Magnetic lines of force always cross each other. Is the given statement true or false? Justify.
State whether the following statement is True or False.
The magnetic lines of force around a bar magnet mutually attract each other.
A particle moving towards south in a vertically downward magnetic field is deflected toward the east. What is the sign of the charge on the particle?
What is the relationship between an electric current and a magnetic field ?
Match the magnetic field lines given below to the types given on the right side of the conductor
The figure shows a circuit containing a coil wound over a long and hollow thin tube. Draw the magnetic field lines of force inside the coil and also their direction.
The polarity of the faces of the coil depends on the direction of current and is obtained by a rule known as "The Clock Rule".
According to this rule "When an observer, looking at the face of the coil, finds the current to be flowing in the anti-clockwise direction, then the face of the coil will behave like the north pole. While if the current is in the clockwise direction, the face of the coil will behave like South Pole.
Hence the face $$B$$ behaves like South Pole and face $$A$$ behaves like North Pole.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil (ii) withdrawn from inside the coil (iii) held stationary inside the coil.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by strong magnetic field to your right side. What is the direction of magnetic field?
___________ is present around the magnet.
When a current carrying conductor is placed in a magnetic field, a mechanical force is exerted on the conductor which can make the conductor move.
The lines of magnetic induction due to a straight current carrying conductor are ________.
The direction of magnetic field on the conductor in Fleming's left hand rule is represented by _________ finger.
Accoording to Fleming's left hand rule Forefinger/ first finger represents directin of Magnetic field.
Are the magnetic field lines closed? Explain.
The field lines are closed curves as they start from north pole to south pole outside and south pole to north pole inside.
(i) Two sets A and B, of three bulbs each, are glowing in two separate rooms. When one of the bulbs in set A is fused, the other two bulbs also cease to glow. But in set B, when one bulb fuses, the other two bulbs continue to glow. explain why this phenomenon occurs.(ii) Why do we prefer arrangements of Set B for house circuiting?
Rajkumar said to you that the magnetic field lines are open and they start at north pole of bar magnet and end at south pole. What questions do you ask Rajkumar to correct him by saying field lines are closed?
Give reasons for the following.
In the experiment conducted by Faraday the induced electric current was not DC.
Faraday connected the coil to a galvanometer, and moved the magnet back and forth inside the cylinder. Lenz's law state that the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field. Since, the magnetic field is first increasing and then decreasing. Hence, the induced current also changes the direction.
Hence, the induced current in the Faraday's experiment was not DC.
How do you verify experimentally that the current carrying conductor experiences a force when it is kept in magnetic field?
An arrangement of conductor carrying current and a magnet is used as
1) Here the copper wire is passed through splits of wooden sticks.
2) The wire is supplied with current.
3) A horse shoe magnet is brought near it.
4) There is displacement in the wire due to force experienced due to magnetic and electric field.
$$(i)$$ Why does a current-carrying freely suspended solenoid rest along a particular direction?
$$(ii)$$ State the direction in which it rests.
Collect information of experiments done by Faraday.
Michael Faraday discovered electromagnetic induction in 1831. He hypothesized that changing magnetic field is necessary to induce current in a nearby circuit. In his experiment as shown in figure(1), he moved a magnet back and forth inside the coil. When he moves the magnet back and forth, he noticed that the galvanometer needle moves, indicating that a current is induced in the coil. Notice also that the needle immediately returns to zero when the magnet is not moving. Faraday confirmed that a moving magnetic field is necessary in order for electromagnetic induction to occur.
Identify the odd one out :
Magnet, Solenoid, Compass needle, Oven.
(a) Write Fleming's left-hand rule for the direction of force on a current carrying conductor placed in a magnetic field.
(b) Draw a diagram to show lines of magnetic field inside and around a current carrying solenoid.
(c) Write the names of four devices where current carrying conductor is used along with magnetic fields.
(a) According to Fleming's left-hand rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of the electric current, then the thumb will point in the direction of motion or the force acting on the conductor.
(b) The diagram is shown to demonstrate the lines of magnetic field inside and around a current carrying solenoid.
(c) Devices that use current-carrying conductors and magnetic fields are electric motor, electric generator, loudspeakers and microphones.
Correct the mistakes, if any, in the following statements:
(a) Magnetic field is a quantity that has magnitude only.
(b) The magnetic field lines emerge from the south pole and merge at the north pole.
What should be the angle between thumb (main) finger, forefinger and central finger in Fleming's left hand rule? What does each finger indicate?
Magnetic lines form continuous closed loops. Why?
Raman's air-conditioner consumes 2160 W of power when a current of 9.0 A passes through it.
i) What is the voltage drop when the air-conditioner is running?
ii) How does this compare to the usual household voltage?
iii) What would happen if Raman tried connecting his air-conditioner to a 120 V line?
Write Fleming's left hand rule.
Correct the mistakes, if any, in the following statements.
i) The magnetic field is a quantity that has magnitude only.
ii) Outside the bar magnet, the magnetic field lines emerge from the south pole and merge at the north pole.
$$(i)$$ The magnetic field is a vector quantity that has magnitude as as well as direction.
$$(ii)$$ Outside the bar magnet, the magnetic field lines emerge from the north pole and merge at the south pole.
What is the principle of Electric motor?
Draw a diagram of the magnetic field lines produced by a(a) Bar magnet (b) Horse-shoe magnet.
Name the colour code of the wire which is connected to the metallic body of an appliance.
What will happen while placing a current-carrying conductor in a magnetic field? Explain.
State Fleming's left hand rule.
Part1: Why we use Fleming's left-hand rule:
When the magnetic field direction and current direction are known, Fleming's Left-Hand Rule is a simple and accurate approach to find the direction of force/motion of the conductor in an electric motor.
Part2: Fleming's left-hand rule:
When the magnetic field direction and current direction are known, Fleming's Left-Hand Rule is a simple and accurate approach to find the direction of force/motion of the conductor in an electric motor.
Part2: Fleming's left-hand rule:
- Fleming's left-hand rule can be stated as stretching the forefinger, middle finger, and thumb of the right hand such that they are mutually perpendicular to each other.
- Here, the forefinger indicates the direction of the magnetic field,
- The middle finger indicates the direction of current in the conductor
- The thumb shows the direction of the force exerted on the conductor.
Draw magnetic field lines around a bar magnet.
List the properties of magnetic lines of force.
The figure shows magnetic field lines around a bar magnet.
- The magnetic field lines form a closed loop.
- No two magnetic field lines cross each other.
Explain the construction of a motor with a diagram.
An electric motor is a device which converts electrical energy into mechanical energy. The principle behind the electric motor is based on Fleming’s left hand rule.
Working: When a current is
allowed to flow through the coil PQRS the coil starts rotating anti-clockwise.
This happens because a downward force acts on length PQ and at the same time,
an upward force acts on length RS. As a result, the coil rotates anti-clockwise.
Current in the length PQ flows from P to Q and the magnetic
field acts from left to right, normal to length PQ. Therefore, according to
Fleming’s left hand rule, a downward force acts on the length PQ. Similarly at
an upward force acts on the length RS. These two forces cause the coil to rotate
anti-clockwise.
When coil complete half rotation, the position of PQ and RS
interchange. The half-ring D comes in contact with brush A and half-ring C
comes in contact with brush B. therefore the direction of current in the coil
PQRS gets reversed. Now the current flows through the coil in the direction
SRQP. The direction of current through the coil PQRS reverse after every
half rotation. As a result, the coil rotates in same direction. The split rings
help to reverse the direction of current in the circuit. These are called the
commutator.
Justify the following statements.
a) Two magnetic field lines never intersect each other.
b) Magnetic field lines are closed curves.
The magnetic induction at the centre of a solenoid is $$B$$. If the length of the solenoid is reduced to half and the same wire is wound in two layers the new magnetic induction is:
$$\textbf{Strength of the Magnetic Fileds at the centre of the solenoid is given by:}$$
$$B = {\mu _0 nI}$$
Here,
$$I= $$ Current flowing through the loop and
$$n= $$ No. of the turns per unit of the length
Here, magnetic field at center of the Solenoid is directly proportional to the current flowing through the Solenoid and number of the turns in solenoid.
$$B\propto
I$$ and $$B\propto n$$ 
Now, the length of the solenoid is halved, the number of turns will be doubled as the same wire is wound in two layers
i.e $$n'=2n$$
then $$B'$$ $$=2B$$
Hence, Magnetic filed at the center of the solenoid became two times than its previous value.
Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?
Draw the pattern of magnetic field lines through and around a current-carrying wire. Make the direction of (i) electric current in the wire (ii) magnetic field lines.
How would the strength of magnetic field due to current, carrying loop be affected if
(a) radius of the loop is reduced to half its original value?
(b) strength of current through the wire is doubled?
How would the strength of magnetic field due to current, carrying loop be affected if
(a) radius of the loop is reduced to half its original value?
(b) strength of current through the wire is doubled?
Step1: Draw figure of direction electric current and magnetic field
Step2:Show how the magnetic field affected
A long straight wire AB carries a current I. A proton P levels with a speed V, parallel to the wire at a distance d from it in a direction opposite to the current. What is the force experienced by the proton and what is its direction?
What does the pattern of field lines in the side the solenoid indicate?
When magnetic field lines are drawn around a current carrying circular loop, it has been observed that they are closed tc its axis. But these lines keeps on diverging as we move away from the centre. Explain this observation.
Name and state the rule to determine the direction of a force experienced by a straight conductor carrying placed in a magnetic field that is perpendicular to it.
The direction of the force experienced by
current carrying straight conductor placed in
mag. field which is given perpendicular to
it is given by Fleming's left hand Rule.
Two magnets are lying side by side as shown below. Draw magnetic field lines between Poles $$\mathrm { P }$$ and $$\mathrm { Q }$$ .
$$\textbf{Magnetic Fileds lines:}$$
$$\bullet$$ Magnetic fileds line emerge Out from the north pole and emerge In at South pole of the a Bar Magnet. 
$$\bullet$$ Externally, they move from north pole of a magnet to its south pole. Hence magnetic fields line for two magnets will be as shown below:
What is the usual current rating of the fuse wire in the line to feed Lights and fans ?
Answer the following Questions:
Write the characteristic of magnetic field lines.
Characteristics of magnetic field lines are :
- They never cross each other.
- Their density decreases when they move from an area of higher permeability to an area of lower permeability.
- Their density decreases with increasing distance from the poles.
- They flow from the south pole to the north pole within the material and north pole to south pole outside.
- The tangent to the magnetic field lines at any point gives the direction of the magnetic field at that point
How will you find the polarity of a current carrying solenoid ?
What is the current rating of an electric appliance of a 2kW power rating when connected to a $$200\ V$$ source?
Explain Fleming's left hand rule with the help of labelled diagram.
Fleming’s left-hand rule: Hold the forefinger, the centre finger and the thumb of your left hand to right angles to one other. Adjust your hand in such a way that the forefinger points in the direction of magnetic field and the and the centre finger points in the direction of the current, then the direction in which thumb points, gives the direction of the force acting on the conductor.
Name the rule for finding the direction of the magnetic field produced by a straight current-carrying conductor.
Maxwell's right hand thumb rule is used for finding the direction of the magnetic field produced by a straight current-carrying conductor. It states that , When the conductor is held in your right hand, such that the direction of thumb points in the direction of the current, then the curled fingers give the direction of the magnetic field.
Which effect of current can be utilized in detecting a current-carrying wire concealed in a wall?
The diagram shows a bar magnet surrounded by four plotting compasses. Copy the diagram and mark in the direction of the compass needle for each of the cases $$B, C$$ and $$D$$.
The diagram for the direction of the compass needles is shown in figure.
What is a magnetic field? How can the direction of magnetic field lines at a place be determined?
State any two properties of magnetic field lines.
What are the two ways in which you can trace the magnetic field pattern of the bar magnet?
Explain why, two magnetic field line do not intersect each other.
Draw a diagram to show the magnetic fields lines around a bar magnet.
Magnetic fields lines around a bar magnet.
The figure given above shows the magnetic field between two magnets:
Copy the diagram and label the other poles of the magnets.
The diagram representing the poles of the magnet is as shown.
In magnet 2, the field lines originate from its left pole so it must be the $$North$$ pole.
The other pole in magnet 1 and 2 is obviously the $$South$$ pole.
What conclusion do you get from the observation that a current-carrying wire deflects a compass needle placed near it?
Fill in the following blanks with suitable words:
The lines of _____ round a straight current-carrying conductor are in the shape of _____.
The lines of magnetic field round a straight current-carrying conductor are in the shape of concentric circles.
In a statement of Fleming's left-hand rule, what do the following represent?
Direction of forefinger.
The direction of forefinger shows the direction of the magnetic field according to the Fleming's left-hand rule.
In the straight wire $$A$$, current is flowing in the vertically downward direction whereas in wire $$B$$ the current is flowing in the vertically upwards direction. What is the direction of magnetic field around the wire $$A$$ and wire $$B$$?
Name the rule which have used to get the answer.
Around the wire $$A$$, the direction of magnetic field will be in clockwise direction whereas around the wire $$B$$, the magnetic field will be in anti-clockwise direction.
We have used Maxwell's right hand thumb rule here to determine the direction of magnetic field.
Fill in the following blanks with suitable words:
For a current-carrying solenoid, the magnetic field is like that of a ______.
For a current-carrying solenoid, the magnetic field is like that of a bar magnet.
For fleming's left-hand rule, write down the three things that are $$90^o$$ to each other, and next to each one write down the finger of thumb that represents it.
According to Fleming’s left-hand rule, stretch the thumb, forefinger, and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of the magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
Name and state the rule to determine the direction of the magnetic field around a straight current-carrying conductor.
State the form of magnetic field lines around a straight current-carrying conductor.
In a statement of Fleming's left-hand rule, what do the following represent?
Directions of thumb.
According to Fleming’s left-hand rule, stretch the thumb,
forefinger and middle finger of your left hand
such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second
finger in the direction of the current, then the thumb will point in the direction of motion or
the force acting on the conductor.
The direction of the thumb represents the force acting on the conductor.
Draw a sketch to show the magnetic lines of force due to a current-carrying straight conductor.
The magnetic field lines due to a current-carrying conductor are as shown in the figure.
What happens when a current carrying conductor is placed in a magnetic field?
State Fleming's left-hand rule. Explain it with help of labelled diagrams.
According to Fleming's left-hand rule, stretch the thumb,
forefinger and middle finger of your left hand
such that they are mutually perpendicular
as shown in the figure. If the first finger points in the direction of the magnetic field and the second
finger in the direction of the current, then the thumb will point in the direction of motion or
the force acting on the conductor.
What is the function of brushes in an electric generator?
State and explain Maxwell's right-hand thumb rule.
According to Maxwell's right hand thumb rule. Imagine that you are grasping the current carrying wire in your right hand so that your thumb points in the direction of current, then the direction in which your fingers encircle the we will give the direction of magnetic field lines around the wire.
Let $$AB$$ be the straight wire carrying current in the vertically upward direction from $$A$$ to $$B$$. To find out the direction of the magnetic field lines produced by this current, we imagine that we are grasping the current carrying wire in our right hand as shown in fig. so that our thumb points in the direction of current towards $$B$$.
Let $$AB$$ be the straight wire carrying current in the vertically upward direction from $$A$$ to $$B$$. To find out the direction of the magnetic field lines produced by this current, we imagine that we are grasping the current carrying wire in our right hand as shown in fig. so that our thumb points in the direction of current towards $$B$$.
Now, the direction in which our fingers are folded gives the direction of magnetic field lines. In this case, the direction of magnetic field lines is in the anticlockwise direction.
What type of core should be put inside a current-carrying solenoid to make an electromagnet?
State two ways to increase the force on a current carrying conductor in a magnetic field.
The magnetic field associated with a current carrying straight conductor is in anticlockwise direction. If the conductor was held along the east-west direction, what will be the direction of current through it? Name and state the rule applied to determine the direction of current?
Draw the labelled diagram of an $$A.C.$$ generator. With the help of this diagram, explain the construction and working of an $$A.C.$$ generator.
Construction:-
A simple $$AC$$ generator consists of a rectangular coil $$ABCD$$ which can be rotated rapidly between the poles $$N$$ and $$S$$ of a strong horseshoe-type permanent magnet $$M$$. The coil is made of a large number of turns of insulated copper wire. The two ends $$A$$ and $$D$$ of the coil are connected to two circular piece of copper metal called slip rings $$R_{1}$$ and $$R_{2}$$. As the slip rings rotate with the coil, the two fixed pieces of carbon called brushes $$B_{1}$$ and $$B_{2}$$ keep contact with them, So, the current produced in the rotating coil can be tapped out through slip rings into the carbon brushes. The outer ends of carbon brushes are connected to a galvanometer to show the flow of current in the external circuit.
Working:-
Suppose the coil $$ABCD$$, which is initially in the horizontal position is rotated in the anticlockwise direction. The side $$AB$$ of the coil moves down and side $$CD$$ moves up. Due to this Induced current is produced in both the sides, which flows in the direction $$BADC$$ (according to Fleming's right hand rule). Thus, in the first half rotation, the current in the external circuit flows from brush $$B_{1}$$ and $$B_{2}$$. After half revolution sides $$AB$$ and $$CD$$ will interchange their positions. So, side $$AB$$ starts moving up and side $$CD$$ starts moving down. As a result direction of induced current in the coil is reversed and flows in the direction $$CDAB$$. The current in the external circuit flows from brush $$B_{2}$$ to $$B_{1}$$.
A simple $$AC$$ generator consists of a rectangular coil $$ABCD$$ which can be rotated rapidly between the poles $$N$$ and $$S$$ of a strong horseshoe-type permanent magnet $$M$$. The coil is made of a large number of turns of insulated copper wire. The two ends $$A$$ and $$D$$ of the coil are connected to two circular piece of copper metal called slip rings $$R_{1}$$ and $$R_{2}$$. As the slip rings rotate with the coil, the two fixed pieces of carbon called brushes $$B_{1}$$ and $$B_{2}$$ keep contact with them, So, the current produced in the rotating coil can be tapped out through slip rings into the carbon brushes. The outer ends of carbon brushes are connected to a galvanometer to show the flow of current in the external circuit.
Working:-
Suppose the coil $$ABCD$$, which is initially in the horizontal position is rotated in the anticlockwise direction. The side $$AB$$ of the coil moves down and side $$CD$$ moves up. Due to this Induced current is produced in both the sides, which flows in the direction $$BADC$$ (according to Fleming's right hand rule). Thus, in the first half rotation, the current in the external circuit flows from brush $$B_{1}$$ and $$B_{2}$$. After half revolution sides $$AB$$ and $$CD$$ will interchange their positions. So, side $$AB$$ starts moving up and side $$CD$$ starts moving down. As a result direction of induced current in the coil is reversed and flows in the direction $$CDAB$$. The current in the external circuit flows from brush $$B_{2}$$ to $$B_{1}$$.
When a wire is moved up and down in a magnetic field, a current is induced in the wire. What is this phenomenon known as?
Explain the principle of an electric generator.
State two ways in which the current induced in the coil of generator could be increased.
What is the electric potential of the neutral wire in a mains supply cable?
What do you understand by the term electromagnetic induction? Explain with the help of a diagram.
The production of electricity from magnetism is known as electromagnetic induction. Let us move a wire $$AB$$ upward rapidly between the poles of the horseshoe magnet. When the wire is moved up, there is a deflection in the galvanometer pointer which shows a current is produced in the wire $$AB$$ momentarily. Thus as the wire is moved up through the magnetic field, an electric current is produced in it.
The figure shows a long solenoid , a cylindrical coil of a number of turns of insulated copper wire , connected to a battery through an ammeter A and a rheostat Rh.
Draw the magnetic field lines inside the solenoid and indicate their direction. Are magnetic field lines closed ?
Yes , magnetic field lines form closed loops and inside the solenoid they go from south to north pole and outside the solenoid it goes from north to south pole.
What is meant by a magnetic field ?
Magnetic field is the area in which the magnetic strength of a magnet can be felt by a magnetic material , inside this field the magnet can either attract or repel the magnetic substances .
The figure shows a long solenoid, a cylindrical coil of a number of turns of insulated copper wire, connected to a battery through an ammeter $$A$$ and a rheostat $$Rh.$$
Which end of the solenoid is an N-pole and which end is an S-pole?
Point P is the south pole and point Q is the North pole because of the specified direction of the current flowing in the solenoid.
By using right-hand thumb rule, when we curl our fingers along the direction of current, our thumb points towards point Q so it is North pole.
How can a magnetic field be produced without using a magnet?
Write one application of the following:
Right-Hand Thumb Rule
What happens to the force experienced by a current carrying conductor in a uniform magnetic field, when placed parallel to the magnetic field?
What happens to the force experienced by a current carrying conductor in a uniform magnetic field, when placed perpendicular to the magnetic field?
The magnetic force on a moving proton acts towards north in a horizontal plane. If the proton is moving vertically upward then what will be the direction of magnetic field?
State the rule to determine the direction of a magnetic field produced around a straight conductor carrying current.
State the rule to determine the direction of a force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.
Both alternating current and direct current are measured in Amperes. But how is Ampere defined for an alternating current?
State the rule to determine the direction of a force experienced by a current-carrying straight conductor placed in a magnetic field that is perpendicular to it.
The direction of the magnetic force acting on a current wire placed in a magnetic field is by Fleming's left-hand rule.
According to Fleming's Left-Hand rule:- If we arrange our left hand's thumb, index finger, and middle finger mutually perpendicular to each other. And if we put our index finger in the direction of the magnetic field applied and middle finger in direction of electric current then the thumb will point in the direction of the magnetic force.
According to Fleming's Left-Hand rule:- If we arrange our left hand's thumb, index finger, and middle finger mutually perpendicular to each other. And if we put our index finger in the direction of the magnetic field applied and middle finger in direction of electric current then the thumb will point in the direction of the magnetic force.
Identify the poles of the magnet in the figure (a) and (b) shown below.
The magnetic field lines emerge from north pole and merge at the south pole
Name the device which converts mechanical energy into electrical energy.
Sketch the magnetic field for a circular current loop.
Show, with the help of a diagram, the nature of field lines of the magnetic field around a current-carrying straight conductor.
The figure is as shown.
The nature of field lines of the magnetic field around a current-carrying straight conductor is concentric circles.
How does the strength of the Magnetic field at the centre of a circular coil of a wire depend on: (a) radius of the coil (b) number of turns in the coil.
Why is electromagnetic induction so called?
When a bar magnet is pushed towards ( or away ) from the coil connected to a galvanometer, the pointer in the galvanometer deflects. Identify the phenomenon causing this deflection and write the factors on which the amount and direction of the deflected depends. State the laws describing this phenomenon.
Describe an activity with labelled diagram to show that a current carrying conductor experiences a force in a magnetic field.
In the following experiment:
Whenever a current carrying conductor is placed in a magnetic field then the conductor will experience a magnetic force. This happens because the current in the conductor has its own magnetic field and there is also a magnetic field present. So both the field will interact and will result in repulsion or attraction of the conductor wire toward the magnets.
The magnetic force depends on four things:
Amount of current
Strength of magnetic field
Length of the wire which remain in magnetic field
And the angle between the current carrying conductor and magnetic field.
The direction of magnetic force acting on a current wire placed in a magnetic field is given by Fleming's left hand rule.
Whenever a current carrying conductor is placed in a magnetic field then the conductor will experience a magnetic force. This happens because the current in the conductor has its own magnetic field and there is also a magnetic field present. So both the field will interact and will result in repulsion or attraction of the conductor wire toward the magnets.
The magnetic force depends on four things:
Amount of current
Strength of magnetic field
Length of the wire which remain in magnetic field
And the angle between the current carrying conductor and magnetic field.
The direction of magnetic force acting on a current wire placed in a magnetic field is given by Fleming's left hand rule.
In a bar magnet, magnetic attraction is near its ends.
Boojho made an electromagnet by winding 50 turns of wire over an iron screw. Paheli also made an electromagnet by winding 100 turns over a similar iron screw. Which electromagnet will attract more pins? Give reason.
Explain the meaning of the term magnetic field.
The space around the magnet where its influence can be experienced is known as magnetic field.This field is formed by the magnetic lines of force which run from the North pole to the South pole.These lines can be found to be maximum crowded at the two ends of the magnet which are the poles i.e. the North pole and the South pole.
(i) How is the direction of magnetic field at a point determined?
(ii) What is the direction of magnetic field at the centre of a current- carrying circular loop?
Boojho dipped a bar magnet in a heap of iron filings and pulled it out. He found that iron filings got stuck to the magnet as shown in the figure.
Which regions of the magnet have more iron filings sticking to it?
Four identical iron bars were dipped in a heap of iron filings one by one. The figure shows the amount of iron filings sticking to each of them. Which of the iron bar is likely to be the strongest magnet? Justify your answer.
Draw the diagram of a simple electric motor. Label the following parts:
(i) Split rings (ii) Brushes
Whereas the brushes help easy transfer of charge between the coil and the external circuit.
Define the term magnetic field of a magnet. How will you recognize it experimentally?
The space around a magnet in which if a magnetic substance such as small pieces of iron is placed, they get attracted to the magnet, which is called the magnetic field. Recognition of the magnetic field around a magnet: If a magnet Is placed below a sheet of stiff paper and some iron filings are spread on it, then on tapping the sheet gently. they are on filings are found to arrange themselves in a definite pattern as shown in the figure.
Complete the following sentence;
...... energy is converted into ........ energy by an electric motor.
State two ways by which the magnetic field due to a solenoid can be made stronger.
State condition when magnitude of force on a current carrying conductor placed in a magnetic field is (a) Zero (b) maximum.
Name and state the law which is used to determine the direction of force on a current carrying conductor placed in a magnetic field.
Draw a diagram showing the directions of the magnetic field lines due to a straight wire carrying current.
The diagram is showing the directions of the magnetic field lines due to a straight wire carrying current and the direction of the current in the wire.
Complete the following sentences:
(a) When current flows in a wire, it creates ............
(b) A current-carrying solenoid behaves like a ..............
(c) A current-carrying solenoid when freely suspended, always rests in .......... direction.
Name two appliances in which an electric motor is used.
What is an electric motor? State its principle.
State two ways by which the speed of rotation of an electric motor can be increased?
Name and state the principle of a simple a.c. generator. What is its use?
The figure shows two bulb with switches and fuse connected to mains through a socket.
a) Label each component
b) Name and state the colour of insulation of each wire 1,2 and 3.
c) How are the two bulbs joined ?In series or in parallel?
(a) All components have been named as given in figure.
b)| Wire no | Wire name | Colour (Old convention) | Colour (New convention) |
| 1 | Neutral wire | Black | Light blue |
| 2 | Earth wire | Green | Green or yellow |
| 3 | Live wire | Red | Brown |
A power circuit uses a cable having three different wires.
a) Name the three wires of the cable.
b) To which of the two wires should the heating element of an electric geyser be connected?
c) To which wire should the metal case of the geyser be connected?
d) To which wire should the switch and fuse be connected?
In which of the following cases does electromagnetic induction occur?
(i) A current is started in a wire held near a loop of wire
(ii) The current is stopped in a wire held near a loop of wire
(iii) A magnet is moved through a loop of wire
(iv) A loop of wire is held near a stationary magnet.
What do you understand by the term magnetic field lines?
(a) What is electromagnetic induction?
(b) Describe one experiment to demonstrate the phenomenon of electromagnetic induction.
(a) Electromagnetic induction: whenever there is change in number of magnetic field lines associated with conductor. an electromotive force is developed between the ends of the conductor which lasts as long as the change is taking place.
(b) Demonstration of the phenomenon of electromagnetic induction:
In the figure:
(i) When the magnet is stationary there is no deflection in galvanometer. The pointer read zero. [Fig. (a)]
(ii) when the magnet with north pole facing the solenoid is moved towards the solenoid. the galvanometer shows a deflection towards the right showing that a current flows in the solenoid in the direction as shown in [Fig (b)]
(iii) As the motion of magnet stops, the pointer of the galvanometer comes to the zero position [Fig (c)]. This shows that the current in the solenoid flows as long as the magnet is moving.
(iv) If the magnet is moved away from the solenoid, the current again flows in the solenoid, but now in a direction opposite to that shown in [Fig. (b)] and therefore the pointer of the galvanometer deflects towards left[ Fig. (d)].
(v) If the magnet is moved away rapidly i.e. with more velocity, the extent of deflection in the galvanometer increases although the direction of deflection remains the same. It shows that more current flows now.
(vi) If the polarity of the magnet is reversed and then the magnet is brought towards the solenoid, the current in solenoid flows in the direction opposite to that shown in Fig (b) and so the pointer of galvanometer deflect towards left [Fig. (e)].
What is tester ?
What is a magnetic field ? State the properties of magnetic field lines.
Will current carrying wire experience a force when kept parallel to the magnetic field ?
What is the difference between AC generator and DC generator ?
Define magnetic field.
State the rule for direction of the magnetic field produced around a carrying conductor. Draw a sketch of a pattern of field lines due to a current flowing through a straight conductor.
Right Hand Thumb Rule use to find direction of magnetic field around current-carrying conductor. To find direction; Hold the wire carrying current in your hand, such that the thumb indicates the direction of current, then the folded fingers will indicate the direction of magnetic field lines surrounding the wire.
Name and state the rule used to determine the direction of magnetic field lines around a current carrying straight conductor.
Direction of magnetic field lines around a current-carrying straight conductor is determined by maxwell's right hand thumb rule.
The Maxwell's right hand thumb rule states that 'When the conductor is held in your right hand, such that the direction of the thumb points the direction of the current then the curled finger gives the direction of the magnetic field lines.
Write four characteristics of magnetic field lines?
Magnetic Field Lines or Magnetic Lines of Force The path made by a compass needle in going it from one end of the bar magnet to another end, then magnetic lines of force may be defined as the curve, the tangent at any point gives the direction of the magnetic field at that point. It may also be defined as the path along which a unit north pole would tend to move if free to do so. Magnetic lines of force are shown in figure 8.7.
Properties
1. The magnetic field lines of a magnet forms continuous closed loops.
2. They start in air from the N-pole and end at the S-pole and then return to the N-pole through the interior of the magnet.
3. The tangent to the field line at a given point represents the direction of the net magnetic field B at that point.
4. The magnetic field lines do not intersect each other. If they do so, that would mean there are two directions of the magnetic field at the point of intersection, which is impossible.
List the properties of magnetic field lines.
Why dont two magnetic field lines intersect each other?
Give the characteristics of magnetic field lines.
Characteristics of magnetic field lines are as follows:
1. Magnetic field lines form closed loops. They start from North Pole and end at South Pole.
2. The magnetic field region where the lines are closer are stronger compared to the regions where the magnetic field lines are far apart.
3. The tangent drawn at any point of the magnetic field line gives the direction of the magnetic field at that point.
4. Magnetic field lines do not intersect each other.
1. Magnetic field lines form closed loops. They start from North Pole and end at South Pole.
2. The magnetic field region where the lines are closer are stronger compared to the regions where the magnetic field lines are far apart.
3. The tangent drawn at any point of the magnetic field line gives the direction of the magnetic field at that point.
4. Magnetic field lines do not intersect each other.
Explain the ‘right-hand thumb rule’ to know the direction of magnetic field.
Right-hand thumb rule: If we hold the wire in the right hand in such a way that the thumb points towards the direction of current then the curled fingers on the wire give the direction of the magnetic field.
What is the principle of an electric motor?
Explanation:
$$\bullet$$An electric motor transforms electrical energy into mechanical energy. It works on the principle of magnetic effects of current. It states when a rectangular coil is placed in a magnetic field and a current is passed through it, a force exerts on the coil resulting rotation of the coil. The direction of the rotation determined by Fleming’s left hand rule.
When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
If the direction of magnetic field and flow of electric current are mutually perpendicular then force experienced by a current-carrying conductor in a magnetic field is largest. The direction of this force is given by the Fleming's left hand rule, which says that if the index finger points in the direction of magnetic field and the middle finger points in the direction of current then the thumb points in the direction of force.
Which sources produce alternating current?
Name some devices in which electric motors are used.
Magnetic field is a quantity that has both .. and .......
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
Principle:
An electric motor is a rotating device that converts electrical energy to mechanical energy working.
Working:
Current in the coil $$ABCD$$ enters from the source battery through conducting brush $$X$$ and flow back to the battery through brush $$Y$$. Notice that the current in the arm $$AB$$ of the coil flows from $$A$$ to $$B$$. In arm $$CD$$ it flows from $$C$$ to $$D$$ that is opposite to the direction of current through arm $$AB$$ on applying Fleming’s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. We find that the force acting on arm $$AB$$ pushes it downwards while the force acting on arm $$CD$$ pushes it upwards.
Thus the coil and the Axle $$O$$, mounted free to turn about an axis, rotate anti-clockwise at half rotation. $$Q$$ makes contact with the brush $$X$$ and $$P$$ with brush $$Y$$. Therefore the current in the coil gets reversed and flows along the path $$DCBA$$. The reversal of current also reverses the direction of force acting on the two arms $$AB$$ and $$CD$$. Thus the arm $$AB$$ of the coil that was earlier pushed down, is now pushed up and the arm $$CD$$ previously pushed up is pushed down. There is a continuous rotation of the coil and to the axle.
Split rings in electric motors acts as a commutator.
An electric motor is a rotating device that converts electrical energy to mechanical energy working.
Working:
Current in the coil $$ABCD$$ enters from the source battery through conducting brush $$X$$ and flow back to the battery through brush $$Y$$. Notice that the current in the arm $$AB$$ of the coil flows from $$A$$ to $$B$$. In arm $$CD$$ it flows from $$C$$ to $$D$$ that is opposite to the direction of current through arm $$AB$$ on applying Fleming’s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. We find that the force acting on arm $$AB$$ pushes it downwards while the force acting on arm $$CD$$ pushes it upwards.
Thus the coil and the Axle $$O$$, mounted free to turn about an axis, rotate anti-clockwise at half rotation. $$Q$$ makes contact with the brush $$X$$ and $$P$$ with brush $$Y$$. Therefore the current in the coil gets reversed and flows along the path $$DCBA$$. The reversal of current also reverses the direction of force acting on the two arms $$AB$$ and $$CD$$. Thus the arm $$AB$$ of the coil that was earlier pushed down, is now pushed up and the arm $$CD$$ previously pushed up is pushed down. There is a continuous rotation of the coil and to the axle.
Split rings in electric motors acts as a commutator.
Which effect of electricity is made used of in a solenoid ?
The solenoid is a long cylindrical coil of wire consisting of a large number of turns bound together very tightly. The current carrying wires produce magnetic field inside the solenoid. Hence here the magnetic effect of current is used.
Write down Fleming's Left Hand Rule.
It is found that whenever a current-carrying conductor is placed inside a magnetic field, a force acts on the conductor in a direction perpendicular to both the directions of the current and the magnetic field.
$$\underline{\text{Rule:}}$$ Hold out your left hand with the forefinger, second finger, and thumb at the right angle to one another. If the forefinger represents the direction of the field and the second finger represents that of the current, then the thumb gives the direction of the force.
Take an insulated copper wire of length not less than $$1\,m$$ and make a solenoid (preferably a wire of gauge number $$26$$). With the help of a magnetic compass check the direction of magnetic field at either ends of the solenoid.
The direction of magnetic field at either ends of the solenoid is different. The needle of the magnetic compass will be attracted by the south pole and repelled by the north pole.
What is meant by magnetic effect of electric current?
The direction of current flow at one end of a solenoid is given above. Which pole of the solenoid is this?
The given direction of the current flow through the solenoid matches with the second figure. Thus, it indicates the south pole.
Which are the components of an electric motor ?
The components of an electric motor are :
Magnetic poles , Armature , Split rings, graphite brushes and axis
___________ current reverses its direction periodically.
Explain an armature ?
Michael Faraday, the Father of electricity, did not even get elementary education. Are you not inspired by the achievements of Farady in the field of science ? Conduct a seminar on "Contributions of Faraday and the hard work behind it."
What is meant by the term, magnetic field? Why does a compass needle show deflection when brought near a bar magnet?
Magnetic field - The region around a magnet in which force of the magnet can be experienced. A compass needle is a small bar magnet so it experiences the force of the other bar magnet when brought near it and deflects.
Complete the figure
The change in magnetic field lines in a coil is the cause of induced electric current in it. Name the underlying phenomenon.
According to Lenz law, if any conductor is kept in a varying magnetic field then EMF is induced in the conductor and when the loop is close the current will follow through the conductor. The phenomena in which it occure is known as Electromagnetic induction.
(a) What is a solenoid? Draw a sketch of the pattern of field lines of the magnetic field through and around a current carrying solenoid.
(b) Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right hand rule to find out the direction of the magnetic field inside and outside the loop.
(a) A solenoid is a long coil (shaped like a cylinder) containing a large number of close turns of insulated copper wire around an iron core. (Refer Fig. 1)
Field lines of the magnetic field through and around a current carrying solenoid is shown in Fig 1.
(b) Direction of magnetic field inside and outside the loop is given as follows (Refer Fig.2)
State Fleming's left-hand rule.
(a) When a current-carrying conductor is placed in a magnetic field, it experiences a magnetic force. The direction of the force can be determined by Fleming's left-hand rule.
$$\text{RULE:}$$
Hold the forefinger, the centre finger and the thumb of the left hand at right angles to one another. If the forefinger points in the direction of the magnetic field, the centre finger points in the direction of the current, then the thumb give the direction of the force acting on the conductor.
We use $$230\,V$$ for our household purpose.
But the power produced at $$11\,kV$$ is transmitted to distant places after increasing the voltage.
Write down one disadvantage of transmitting electricity at high voltage.
The direction of movement of electrons through a magnetic field is depicted. "The force felt by the electrons due to the influence of the magnetic field is into the plane of the paper." Is this statement correct ? Explain based on the Fleming's Left Hand Rule.
Magnetic lines of force of two pairs of magnets are shown in figure A and B. Out of these two figures, which one represents the correct pattern of field lines. Name the poles of magnets facing each other.
Figure B represents the correct pattern of magnetic field lines of a pair of magnets. Figure A does not represent the correct pattern of field lines because magnetic field lines never cross each other.
Since, the magnetic field lines spread outward from the North Pole, hence according to the figure, North poles of both the bar magnets are facing each other.
What is a solenoid? Draw the pattern of magnetic field lines of
(i) A current-carrying solenoid and
(ii) A bar magnet.
A solenoid is a long cylindrical coil containing a large number of closely spaced turns of insulated copper wire.
$$\text{Distinguish between the two fields are}-$$
(a) The strength of the magnetic field due to a solenoid can be changed while the magnetic field strength due to bar magnet cannot be changed.
(b) Solenoid produces magnetic field so long as current flows in its coils while bar magnet produces a permanent magnetic field.
The imaginary lines representing magnetic field around a magnet are known as _________.
How can you convert an A.C. into a D.C. generator?
Write one application of each of the following:
(a) Right-hand thumb rule
(b) Flemings left hand rule
(c) Flemings right hand rule
How is the strength of magnetic field near a straight current carrying conductor
(i) related to the strength of current in the conductor?
(ii) is affected by changing the direction of flow of current in the conductor?
For the current carrying solenoid as shown below, draw magnetic field lines and giving reason explain that out of the three points A,B and C at which point the field strength is maximum and at which point it is minimum.
Answer the question to the point.
What is a solenoid? Give the characteristics of the magnetic field resulting from solenoid?
A solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix.
Characteristics of magnetic field lines from solenoid:
i) They form circular loops.
ii) The field lines resembles to those of a bar magnet.
(a) Describe an activity to demonstrate the pattern of magnetic field lines around a straight conductor carrying current.(b) State the rule to find the direction of magnetic field associated with a current carrying conductor.
(c) What is the shape of a current carrying conductor whose magnetic field pattern resembles that of a bar-magnet ?
(a) Procedure : (Refer Fig. 1)
Attach the thick wire through a hole at the middle of the cardboard and clamp it in a stand.
Attach the ends of the wire through a key, variable resistor and an ammeter on either side of a battery and hold it vertically and perpendicularly to the board.
Spread the iron filings uniformly on the cardboard and place the magnetic needle on the board.
Close the key and tap the cardboard slightly and observe the orientation of iron filings.
(b) Right-Hand Thumb Rule. This rule is used to find the direction of magnetic field due to a straight current carrying wire.
It states that if we hold the current carrying-conductor in the right hand in such a way that the thumb is stretched along the direction of current, then the curly finger around the conductor represent the direction of magnetic field produced by it. This is known as right-hand thumb rule. Direction of Field Lines due to current carrying straight conductor is as shown in fig. 2
(c) Solenoid.
What is meant by solenoid? How does a current carrying solenoid behave? Give its main use.
A straight wire carrying electric current is moving out of plane of paper and is perpendicular to it. What is the direction and type of induced magnetic field?
Induced magnetic field will be in the form of concentric circles in the plane of paper. The direction of the field is given by the right hand thumb rule.
What are magnetic field lines? Justify the following statements
(a) Two magnetic field lines never intersect each other.
(b) Magnetic field lines are closed curves.
What type of core should be put inside a current-carrying solenoid to make an electromagnet?
What is a solenoid? Draw a sketch to show the magnetic field pattern produced by a current carrying solenoid.
A long cylindrical coil if insulated copper wire of large number of circular turns is called Solenoid. And when a current passed through a solenoid. it produced magnetic field around it.
The magnetic field pattern produced by a current carrying Solenoid is similar to the magnetic field produced by a bar magnet.
Observe the figure given above and answer the following questions. If switch K is closed. Then,
(a) Write the special name given to the coil AB which has many circular turns of insulated copper wire.
(b) State the nature of magnetic field inside AB when a current is passed through it.
(c) Redraw the diagram and sketch the pattern of magnetic field lines through and around AB .
(d) What is the effect of placing an iron core inside the coil AB?
(b) The field lines inside the solenoid are in the form of
parallel straight lines. This indicates that the magnetic field is
the same at all points inside the solenoid. That is, the field is
uniform inside the solenoid.
(c) Fig drawn above.
(d) The strong magnetic field produced inside the solenoid will magnetize iron core when placed inside the coil. The magnet so formed is
called an electromagnet.
Which effect of current can be utilised in detecting current carrying wire concealed in a wall?
Explain the difference: AC generator and DC generator.
The diagram shows a bar magnet surrounded by four plotting compasses. Copy the diagram and mark it in the direction of the compass needle for cases B, C, and D.
Needle of Magnetic compass shows the direction of magnetic field. Because from end X magnetic field lines are coming out and from end Y field lines will inter into the magnet. Hence all field lines come out form end X and will inter into the end Y so above image will show the direction of magnetic or compass needle at points B, C and D.
Briefly explain an activity to plot the magnetic field lines around a bar magnet. Sketch the field pattern for the same specifying field directions. A region A has magnetic field lines relatively closer than another region B. Which region has stronger magnetic field. Give reason to support your answer.
1. Take a drawing sheet and fix it on a smooth table with adhesive tape.
2. Place a bar magnet in the middle of the drawing sheet and draw its boundary with a sharp pencil.
3. Place a magnetic compass near one end of the magnet (N-pole) and mark the positions of the two ends (N and S-poles) of the compass needle using a sharp pencil.
4. Shift the compass from this position and place it in such a way that S-pole of its needle is on the point you marked in previous step for N-pole.
5. Again mark the position of the other end (N-pole) of the compass needle.
6. Repeat the steps 4 and 5, till you reach the other end (S-pole) of the bar magnet.
7. Join all the points with a sharp pencil to get a smooth curve.
8. Put the compass at some other points near the N-pole of the magnet and draw another magnetic field lines. Similarly, draw many field lines on both the sides of the bar magnet as shown in figure.
9. Observe the pattern of the magnetic field lines.
Result: Magnetic field lines can be drawn around a bar magnet using a magnetic compass. The field lines do not cross each other.
Region A has stronger magnetic field. This is due to the strength of the field is proportional to the relative closeness of field lines.
2. Place a bar magnet in the middle of the drawing sheet and draw its boundary with a sharp pencil.
3. Place a magnetic compass near one end of the magnet (N-pole) and mark the positions of the two ends (N and S-poles) of the compass needle using a sharp pencil.
4. Shift the compass from this position and place it in such a way that S-pole of its needle is on the point you marked in previous step for N-pole.
5. Again mark the position of the other end (N-pole) of the compass needle.
6. Repeat the steps 4 and 5, till you reach the other end (S-pole) of the bar magnet.
7. Join all the points with a sharp pencil to get a smooth curve.
8. Put the compass at some other points near the N-pole of the magnet and draw another magnetic field lines. Similarly, draw many field lines on both the sides of the bar magnet as shown in figure.
9. Observe the pattern of the magnetic field lines.
Result: Magnetic field lines can be drawn around a bar magnet using a magnetic compass. The field lines do not cross each other.
Region A has stronger magnetic field. This is due to the strength of the field is proportional to the relative closeness of field lines.
(a) Explain an activity to show that a current-carrying conductor experiences a force when placed in a magnetic field.
(b) State the rule which gives the direction of force acting on the conductor..
(c) An electron moves perpendicular to a magnetic field as shown in the figure. What would be the direction of force experienced on the electron?
Briefly explain an activity to plot the magnetic field lines around a straight current carrying conductor. Sketch the field pattern for the same, specifying current and field directions. What happens to the field,
(a) if the strength of the current is decreased?
(b) if the direction of the current is reversed?
The pattern of magnetic field lines around a straight conductor carrying current can be described by the following activity.
(i) Insert vertically a long straight wire carrying an electric current so that it passes through the centre of a horizontal piece of plastic board as shown in figure.
(ii) Take care that the plastic board is fixed and does not move up and down. Now, sprinkle some iron filings onto the plastic board to show the shape of the field.
(iii) You will notice that the iron filings get arranged round the wires in the shape of circles. This is due to the reason that the magnetic field lines around the current carrying straight conductor are circular The iron filings align along these field lines.
(iv) On reversing the direction of flow of current, we observe that the iron filing arrange themselves in circles around the wire showing that the magnetic field lines are still circular in nature. The direction of the magnetic field can be obtained by using a compass. If the current direction is reversed, the direction of the magnetic field is also reversed.
(a) When current through the wire is decreased, field also gets reduced.
(b) When the current is reversed, field also gets reversed in direction.
(i) Insert vertically a long straight wire carrying an electric current so that it passes through the centre of a horizontal piece of plastic board as shown in figure.
(ii) Take care that the plastic board is fixed and does not move up and down. Now, sprinkle some iron filings onto the plastic board to show the shape of the field.
(iii) You will notice that the iron filings get arranged round the wires in the shape of circles. This is due to the reason that the magnetic field lines around the current carrying straight conductor are circular The iron filings align along these field lines.
(iv) On reversing the direction of flow of current, we observe that the iron filing arrange themselves in circles around the wire showing that the magnetic field lines are still circular in nature. The direction of the magnetic field can be obtained by using a compass. If the current direction is reversed, the direction of the magnetic field is also reversed.
(a) When current through the wire is decreased, field also gets reduced.
(b) When the current is reversed, field also gets reversed in direction.
The direction of current flowing in the coil of an electromagnet at its two ends $$X$$ and $$Y$$ are as shown above:
What pole will be the end $$Y$$?
For the coil in the diagram below, when the switch is pressed:
what is the polarity of end $$A$$ ?
What is the shape of field lines inside a current-carrying solenoid? What does the pattern of field lines inside a current-carrying solenoid indicate?
What is a solenoid? Draw the pattern of magnetic field lines of
(i) A current carrying solenoid and
(ii)A bar magnet. List two distinguishing features between the two fields.
It is coil containing many circular terns, there wire are wrapped closely in the shape of a cylinder and it is used as an electromagnet.
It also refers to any device that converts electrical energy to mechanical energy using a solenoid. The device creates a magnetic field from electric current and uses the magnetic field to create linear motion.
In above image:-
1). The magnetic field for the current carrying solenoid
2). For bar magnet.
List of the distinguishing features between the two fields:
a) The poles of the bar magnet do not lie exactly at the end of the magnet but are somewhat inside. In a solenoid, poles can be considered to be lying at the edge.
b) The magnetism retains in the bar magnet naturally but in the solenoid, the magnetism is there so long current flows through it.
c) A magnetic field of a bar magnet emanates from throughout the body of the magnet, with more intensity at the poles. While there is no field emanating from the lateral surface of the solenoid.
The direction of current flowing in the coil of an electromagnet at its two ends $$X$$ and $$Y$$ are as shown below:
What is the polarity of end $$X$$?
The figure shows a solenoid wound on a core of soft iron. Will the end $$A$$ be a $$N$$ pole or $$S$$ pole when the current flows in the direction shown?
Draw a diagram to represent the magnetic field lines along the axis of a current-carrying solenoid mark arrows to show the direction of current in the solenoid and the direction of magnetic field lines.
A coil of many circular turns of insulated copper wire wrapped
closely in the shape of a cylinder is called a solenoid. The pattern
of the magnetic field lines around a current-carrying solenoid is
shown in the figure.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
Describe the experiment that explains the phenomenon of electromagnetic induction and give its conclusions.
1. Make a circular loop of conducting wire and connect a galvanometer with it to record the presence of electric current, as shown in the figure below.
2. Take a bar magnet and keep it stationary near the loop. The galvanometer does not show any deflection (fig a), which means no current is produced in the loop.
3. Next, move the North pole of the magnet rapidly towards the loop. The galvanometer deflects to one side showing the presence of an electric field (fig b).
4. Then take the magnet away from the loop rapidly. Again the galvanometer shows deflection indicating the presence of current, but in opposite direction (fig c).
5. In the same way if the South Pole of the magnet is taken, the deflection in the galvanometer will be opposite to both the above-mentioned cases.
Conclusion:
From the above observation it is clear that whenever there is a relative motion between the coil and the magnet, a current is induced in the coil due to a change in the magnetic flux linked with it.
This phenomenon is known as electromagnetic induction.
2. Take a bar magnet and keep it stationary near the loop. The galvanometer does not show any deflection (fig a), which means no current is produced in the loop.
3. Next, move the North pole of the magnet rapidly towards the loop. The galvanometer deflects to one side showing the presence of an electric field (fig b).
4. Then take the magnet away from the loop rapidly. Again the galvanometer shows deflection indicating the presence of current, but in opposite direction (fig c).
5. In the same way if the South Pole of the magnet is taken, the deflection in the galvanometer will be opposite to both the above-mentioned cases.
Conclusion:
From the above observation it is clear that whenever there is a relative motion between the coil and the magnet, a current is induced in the coil due to a change in the magnetic flux linked with it.
This phenomenon is known as electromagnetic induction.
What is a solenoid ? Give the characteristics of magnetic field resulting from solenoid.
A construction like a coil made by a conducting wire wound closely and separately in form of a cylinder is called a solenoid. as shown in figure below.
The magnetic field resulting from solenoid is shown in the figure above. It is same as that due to a bar magnet. Thus, one end of the solenoid behaves as North Pole and the other end as South Pole. In the inner region of a solenoid, the field lines are parallel indicating that the magnetic field is uniform at every point inside the solenoid.
The strength of the magnetic field produced by a solenoid is directly proportional to the number of turns on the solenoid and the current passing through it.
The magnetic field resulting from solenoid is shown in the figure above. It is same as that due to a bar magnet. Thus, one end of the solenoid behaves as North Pole and the other end as South Pole. In the inner region of a solenoid, the field lines are parallel indicating that the magnetic field is uniform at every point inside the solenoid.
The strength of the magnetic field produced by a solenoid is directly proportional to the number of turns on the solenoid and the current passing through it.
Take an insulated copper wire of length not less than $$1\,m$$ and make a solenoid . It will act as a magnet when current from a cell is passed through it after inserting a soft iron core. What is this device known as?
Draw a circuit diagram to explain the ring system of house wiring. State two advantage of it.
Advantages of ring system over tree system
i) In a ring system the wiring is cheaper than tree system
ii) In ring system the sockets and plugs of same size can be used while in tree system sockets and plugs are of different size.
iii) In ring system, each appliance has a separate fuse due to which if there is a fault and the fuse of one appliance burns it does not affect other appliances; while in a tree system when fuse in one distribution lines blows,it disconnects all the appliances connected to that distribution circuit.
i) In a ring system the wiring is cheaper than tree system
ii) In ring system the sockets and plugs of same size can be used while in tree system sockets and plugs are of different size.
iii) In ring system, each appliance has a separate fuse due to which if there is a fault and the fuse of one appliance burns it does not affect other appliances; while in a tree system when fuse in one distribution lines blows,it disconnects all the appliances connected to that distribution circuit.
Describe the principle, construction and working of an electric motor along with a figure.
Construction:
It consists of a loop $$ABCD$$ of an insulated copper wire placed in a permanent magnetic field such that $$AB$$ and $$CD$$ remain perpendicular to the magnetic field. The ends of the wire are connected to two semicircular rings. The inner part of both the rings is insulated. The rings are attached on an axle such that they can rotate easily on it. The outer position of the ring is in contact with stationary brushes which in turn are connected to an external circuit.
Working:
The plane of the coil is horizontal and the split ring $$S_{1}$$ touches the brush $$B_{1}$$ while the split ring $$S_{2}$$ touches the brush $$B_{2}$$. The brush $$B_{1}$$ is connected to the anode of the d.c. battery while the brush $$B_{2}$$ is connected to the cathode. The current flows in the coil in the direction $$ABCD$$. The arms $$BC$$ and $$DA$$ being parallel to the magnetic field experience no force.
According to Fleming’s left hand rule, force $$‘F’$$ acting on the arm $$AB$$, is inward and perpendicular to the plane of the coil and the force on the arm $$CD$$ is in just in the opposite direction. The forces on the arms $$AB$$ and $$CD$$ being equal and opposite form an anticlockwise couple, due to which the coil begins to rotate. It rotates in such a way that the arm $$AB$$ goes in and the arm $$CD$$ comes out.
When the coil reaches the vertical position, the couple becomes zero since the forces on the arms now become collinear. However, due to the inertia of motion, the coil does not stop in this position. As the coil passes from the vertical the split ring $$S_{1}$$ comes in contact with the brush $$B_{2}$$, while the split ring $$S_{2}$$ comes in contact with the brush $$B_{1}$$. Now the current flows through the coil in the direction $$DCBA$$ and the forces acting on the arms $$DC$$ and $$AB$$ of the coil again form an anticlockwise, couple due to which the coil remains rotating in the same direction. Thus, whenever the coil comes in the vertical position, the direction of the current through the coil reverses and the coil continues to rotate in the same direction.
It consists of a loop $$ABCD$$ of an insulated copper wire placed in a permanent magnetic field such that $$AB$$ and $$CD$$ remain perpendicular to the magnetic field. The ends of the wire are connected to two semicircular rings. The inner part of both the rings is insulated. The rings are attached on an axle such that they can rotate easily on it. The outer position of the ring is in contact with stationary brushes which in turn are connected to an external circuit.
Working:
The plane of the coil is horizontal and the split ring $$S_{1}$$ touches the brush $$B_{1}$$ while the split ring $$S_{2}$$ touches the brush $$B_{2}$$. The brush $$B_{1}$$ is connected to the anode of the d.c. battery while the brush $$B_{2}$$ is connected to the cathode. The current flows in the coil in the direction $$ABCD$$. The arms $$BC$$ and $$DA$$ being parallel to the magnetic field experience no force.
According to Fleming’s left hand rule, force $$‘F’$$ acting on the arm $$AB$$, is inward and perpendicular to the plane of the coil and the force on the arm $$CD$$ is in just in the opposite direction. The forces on the arms $$AB$$ and $$CD$$ being equal and opposite form an anticlockwise couple, due to which the coil begins to rotate. It rotates in such a way that the arm $$AB$$ goes in and the arm $$CD$$ comes out.
When the coil reaches the vertical position, the couple becomes zero since the forces on the arms now become collinear. However, due to the inertia of motion, the coil does not stop in this position. As the coil passes from the vertical the split ring $$S_{1}$$ comes in contact with the brush $$B_{2}$$, while the split ring $$S_{2}$$ comes in contact with the brush $$B_{1}$$. Now the current flows through the coil in the direction $$DCBA$$ and the forces acting on the arms $$DC$$ and $$AB$$ of the coil again form an anticlockwise, couple due to which the coil remains rotating in the same direction. Thus, whenever the coil comes in the vertical position, the direction of the current through the coil reverses and the coil continues to rotate in the same direction.
Will the compass needle show deflection when the switch in the circuit shown in above figure is closed?
What is the difference observed in the direction of magnetic field lines on reversing the current through the solenoid?
State the Motor Rule. If the directions of current in the conductor and the magnetic field are the same, in which way will the conductor move ?
What are the properties of magnetic field lines?
Analyze the above figure and find the answer to the question given below.
What are the colors used for wires in phase, neutral and earth lines ?
The compass needle behaves as a _______.
The diagram given below represents magnetic field caused by current carrying conductor. Identify the nature of the coil.
Draw the magnetic field lines through and around a single loop of wire carrying electric current.
An electric motor is a ________ device used for converting electrical energy to mechanical energy.
The magnetic field produced by a current-carrying wire at a given point depends directly on the _______ passing through it.
Split ring acts as ________ .
Split ring acts as commutator. The split ring in the electric motor also known as a commutator reverses the direction of current flowing through the coil after every half rotation of the coil. Due to this the coil continues to rotate in the same direction.
The combination of soft iron core and coil is called _________.
An electric motor is a device that converts __________ to __________ .
Name A & B in the given diagram.
The figure shows a split ring commutator and the two carbon brushes in their respective positions.
What can you say about carbon brush and spilt ring commutator?
Label the diagram of electric motor.
Name C & D and mention the use of this component.
What is the advantage of using AC over DC?
DC generator generates _____________.
In AC generator, after every half rotation, __________ in the respective arm changes, thereby generating an alternating current.
(a) Two straight long parallel conductors carry currents $$I_1$$ and $$I_2$$ in the same direction. Deduce the expression for the force per unit length between them. Depict the pattern of magnetic field lines around them.
(b) A rectangular current carrying loop EFGH is kept in a uniform magnetic field as shown in the figure.
(i) What is the direction of the magnetic moment of the current loop?
(ii) When is the torque acting on the loop
(A) maximum,
(B) zero?
[see image 1]
Consider two infinitely long parallel conductors carrying current $$I_1$$ and $$I_2$$ in the same direction.
Let d be the distance of separation between these two conductors.
[see image 2]
$$B_1 = \dfrac{\mu_0I_2}{2\pi d}$$
$$F_2 = I_2 \times l_2 \times B_1 \, \sin \theta$$ $$(\sin \theta = 1]$$
$$\Rightarrow F_2 = I_2 \times l_2 \times \dfrac{\mu_0 \times l_1}{2\pi d}$$
Force per unit length,
$$F = \dfrac{\mu_0 I_1I_2}{2\pi d}, B_2 = \dfrac{\mu_0I_2}{2\pi d}$$
$$F_1 = I_1 \times l_1 \times B_2 \ \sin \theta$$
$$\Rightarrow F_1 = \dfrac{\mu_0I_1 I_2l_1}{2\pi d}$$
$$\because$$ Force per unit length, $$F = \dfrac{\mu_0 I_1I_2}{2\pi d}$$
Hence, force is attractive in nature.
Ampere : Ampere is that current which is if maintained in two infinitely long parallel conductors of negligible cross-sectional area separated by 1 metre in vacuum causes a force of $$2 \times 10_{-7} N$$ on each metre of the other wire.
Then current flowing is $$1A$$
[see image 3]
(i) Magnetic moment will be out of the plane from the surface HEFG.
(ii) Torque
(A) Torque is maximum when MII B i.e., when it gets rotated by $$90^o$$.
(B) Torque is minimum when M and B are at $$270^o$$ to each other.
Consider two infinitely long parallel conductors carrying current $$I_1$$ and $$I_2$$ in the same direction.
Let d be the distance of separation between these two conductors.
[see image 2]
$$B_1 = \dfrac{\mu_0I_2}{2\pi d}$$
$$F_2 = I_2 \times l_2 \times B_1 \, \sin \theta$$ $$(\sin \theta = 1]$$
$$\Rightarrow F_2 = I_2 \times l_2 \times \dfrac{\mu_0 \times l_1}{2\pi d}$$
Force per unit length,
$$F = \dfrac{\mu_0 I_1I_2}{2\pi d}, B_2 = \dfrac{\mu_0I_2}{2\pi d}$$
$$F_1 = I_1 \times l_1 \times B_2 \ \sin \theta$$
$$\Rightarrow F_1 = \dfrac{\mu_0I_1 I_2l_1}{2\pi d}$$
$$\because$$ Force per unit length, $$F = \dfrac{\mu_0 I_1I_2}{2\pi d}$$
Hence, force is attractive in nature.
Ampere : Ampere is that current which is if maintained in two infinitely long parallel conductors of negligible cross-sectional area separated by 1 metre in vacuum causes a force of $$2 \times 10_{-7} N$$ on each metre of the other wire.
Then current flowing is $$1A$$
[see image 3]
(i) Magnetic moment will be out of the plane from the surface HEFG.
(ii) Torque
(A) Torque is maximum when MII B i.e., when it gets rotated by $$90^o$$.
(B) Torque is minimum when M and B are at $$270^o$$ to each other.
