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CBSE Questions for Class 10 Physics Magnetic Effects Of Electric Current Quiz 11 - MCQExams.com
CBSE
Class 10 Physics
Magnetic Effects Of Electric Current
Quiz 11
The diagram shows a bar magnet surrounded by four plotting compasses.
Which is the North Pole?
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X
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A
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Y
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B
Explanation
When a magnetic compass is kept in the magnetic field the direction compass needle shows the direction of the magnetic field.
In the above image, Compass near the
X -
end shows the outward direction of magnetic field and the Compass near the
Y -
end shows inward direction of magnetic field. Hence
X
end will show the North pole of the magnet and
Y
end will show the North pole of the magnetic field.
Option A.
Take a cardboard and sprinkle some salt and iron filings on it. How will you separate these two?
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Use a bar magnet
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Blow them
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Shake the cardboard
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All of the above.
Explanation
When using a bar magnet the iron filings will stick onto it and will easily be separated.
The region around a magnet, in which the force of magnet can be detected, is called as ________.
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electric current
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poles
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magnetic field
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electromagnetism
Explanation
The region around a magnet, in which the force of magnet can be detected, is called as
magnetic field.
Take a cardboard and sprinkle some iron fillings on it. Bring a bar magnet close to the iron fillings. What do you observe?
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Iron filings stick only on the north pole of a bar magnet
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Iron filings stick only on the south pole of a bar magnet
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Iron filings align themselves along the field lines.
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None of the above.
Explanation
You will observe that the iron filings tend to attract towards the magnet and Iron filings align themselves along the field lines.
The flow of current in a circular wire creates a magnetic field at its centre. How can the existence of this field be detected?
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battery
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solenoid
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right hand thumb rule
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magnetic compass needle
Explanation
The existence of this field can be detected by using a magnetic compass needle at the centre of circular wire and the needle will align itself along the axis of loop.
In a current carrying circular wire,
$$ \mathrm B\;\propto\;\frac1{\mathrm N} $$
where N is no. of turns
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True
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False
Explanation
The statement is False.
In a current carrying circular wire $$\mathrm B\;\propto\;\mathrm N$$
If the number of turns in a current-carrying circular loop is decreased by $$10$$ times, then how will the magnetic field change?
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Increase by $$10$$ times
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Increase by $$5$$ times
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Decrease by $$10$$ times.
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Decrease by $$5$$ times
Explanation
The magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it. Therefore, if there is a circular coil having $$n$$ turns, the field produced is $$n$$ times as large as that produced by a single turn. This is because the current in each circular turn has the same direction and the field due to each turn then just adds up.
If the number of turns in a current-carrying circular loop is decreased by $$10$$ times, then the magnetic field will decrease by $$10$$ times.
The field at the centre of long circular coil carrying current will be curved lines.
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True
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False
Explanation
The statement is false.
The field at the centre of long circular coil carrying current will be straight parallel lines.
Where is the magnetic field strongest in a circular loop?
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On the circumference
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At the centre
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Outside the loop
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Everywhere on the loop
Explanation
The magnetic field produced by a current-carrying straight wire depends inversely on the distance from it. Similarly at every point of a current-carrying circular loop, the concentric circles representing the magnetic field around it would become larger and larger as we move away from the wire. At the center of the circular loop, the arcs of these big circles would appear as straight lines. Every point on the wire carrying current would give rise to the magnetic field appearing as straight lines at the center of the loop.
The direction of the current in the DC generator is always the same and unidirectional because brush $$B1$$ is always in contact with the wire.
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True
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False
Explanation
To get a direct current (DC, which does not change its direction with time), a split-ring type commutator must be used. With this arrangement, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down.
A boy was making a model of an electric bell. He connected the coil in the circuit and switched it on. However, the magnetism produced in the coil was not strong enough. He made some changes in the coil and the circuit was now working.
What changes did the boy make in the coil?
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Decrease in the no. of turns in the coil
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Replaced the coil
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Increase in the number of turns in the coil
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All of the above
Explanation
If we increase the number of turns, the current flowing through it also increases. The magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it.
As we move towards the outer edge of the circular loop, the magnetic field lines appear to be _________.
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Converging
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Diverging
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Straight
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Elliptical
Explanation
As we move towards the outer edge of the circular loop, the magnetic field lines appear to be diverging.
Which of the following figures correctly depicts the direction of magnetic field of a current carrying through a circular loop.
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0%
0%
0%
Explanation
A magnetic field is produced by an electric current flowing through a circular coil of wire. Each small section of current carrying wire contributes to magnetic field lines. At the centre of circular wire, field lines become straight and perpendicular to the plane of coil.
Choose the components for electric motor.
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Brushes
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Axle
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Magnet
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Electricity metre
Explanation
Components for electric motor are Brushes, axle, magnet, etc,
Choose the correct statement/(s).
The strength of the magnetic field produced by a current carrying circular coil can be increased by
Report Question
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increasing the number of turns.
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changing the magnet.
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increasing the current flowing through the coil.
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All of the above
Explanation
The strength of the magnetic field produced by a current carrying circular coil can be increased by
increasing the number of turns.
increasing the current flowing through the coil.
A boy was making a model of electric bell. He connected the coil in the circuit and switched it on. However, the magnetism produced in the coil was not strong enough. He made some changes in the coil and the circuit was now working.
How can you produce strong magnetism without changing the magnet?
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Change the Magnet
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Increase the magnitude of current passing through the coil
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Decrease the no of turns in the coil.
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None of the above.
Explanation
The magnetic effect of current produced is directly proportional to the current in wires due to which this effect is produced.
Hence by increasing the magnitude of current passing through the coil magnetism is increased.
Among the following components of electric motor, which component acts as a commutator?
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Axle
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Magnets
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Brushes
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Split Rings
Explanation
A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine.
Electric motor is used in
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TV
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MP3 player
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Mobile Phone
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mixers
What happens to the strength of the magnetic field if the number of turns is increased?
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Strength of magnetic field increases
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There is no change in the magnetic field
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Strength of magnetic field decreases
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Magnetic field disappears
Explanation
The magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it. Therefore, if there is a circular coil having $$n$$ turns, the field produced is $$n$$ times as large as that produced by a single turn. This is because the current in each circular turn has the same direction and the field due to each turn then just adds up.
The speed of the motor can be increased by:
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Decreasing the current
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Increasing the number of turns in the coil
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Increasing the size of motor
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All of the above
Explanation
The speed of the motor can be increased by increasing the number of turns in the coil.
If we increase the number of turns, the current flowing through it also increases. The magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it.
Why is an armature used in electric motor?
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It enhances magnetic field
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It enhances electric current
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It enhances power of motor
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It enhances speed
Explanation
The combination of soft iron core and coil is called an armature. It is a rectangular iron core wrapped by the copper coil in a motor through which electricity passes and due to magnetic field it experiences a force and rotates and generates mechanical power.It enhances the power of motor.
In electric motor, which rule is used to find the direction of force on a current carrying conductor in a magnetic field?
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Electromagnetic induction
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Right-hand thumb rule
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Fleming's left-hand rule
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None of these
Explanation
In an electric motor, the direction of the force on a current-carrying conductor in a magnetic field is determined by Fleming's left-hand rule.
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 the current, then the thumb will point in the direction of motion or the force acting on the conductor.
A commercial electric motor is different from simple electric motor because it uses permanent magnet.
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True
0%
False
Explanation
The statement is false.
A commercial electric motor is different from simple electric motor because it uses electromagnet in the place of permanent magnet
Which rule is used to find the direction of the induced current?
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Fleming's right hand rule
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Right hand thumb rule
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Fleming's left hand rule
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None of the above
Explanation
Fleming's right-hand rule shows the direction of induced current when a conductor attached to a circuit moves in a magnetic field. It can be used to determine the direction of current in a generator's windings.
What would happen to the direction of rotation of the motor, if the current were reversed.
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direction of the rotation will be changed by 90 degree
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direction of the rotation will be changed by 270 degree
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direction of the rotation would be reversed.
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direction of rotation would remain unchanged.
After half rotation _______ comes in contact with _________, and ______ comes in contact with ________ .
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ring R1, ring R2 & brush B1, brush B2
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ring R1, brush B1 & ring R2, brush B2
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ring R1, brush B2 & ring R2, brush B1
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ring R2, brush B2 & ring R1 , brush B2
Explanation
After half rotation
ring R1
comes in contact with
brush B2
, and
ring R2
comes in contact with
brush B1
.
Frequency of AC mains in India is:
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$$20\ Hz$$
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$$50\ Hz$$
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$$100\ Hz$$
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$$240\ Hz$$
Explanation
The alternating
current reverses its direction periodically.
In India, the AC changes direction
after every $$1/100\ second$$, that is, the frequency of AC is $$50\ Hz$$.
Split rings are used in AC generator.
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True
0%
False
Explanation
Split rings are used in AC generator. The two ends of this coil are connected to the two rings. The inner side of these rings are made insulated. The two conducting stationary brushes are kept pressed separately on the rings.
In India the AC changes direction after every _________ second.
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$$1/50$$
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$$1/150$$
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$$1/100$$
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$$1/1000$$
Explanation
The alternating current reverses its direction periodically. Most power stations constructed these days produce AC. In India, the AC changes direction after every $$\dfrac {1}{100}\ second$$, that is, the frequency of AC is $$50\ Hz$$. An important advantage of AC over DC is that electric power can be transmitted over long distances without much loss of energy.
In DC generator the current produced is unidirectional.
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0%
True
0%
False
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