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CBSE Questions for Class 10 Physics Magnetic Effects Of Electric Current Quiz 7 - MCQExams.com
CBSE
Class 10 Physics
Magnetic Effects Of Electric Current
Quiz 7
Find out the arrow or arrows which give the direction of conventional current flow.
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Arrow A only
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Arrow B only
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Arrow C only
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Arrows A and D
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Arrows B and E
Explanation
Arrow $$A$$ shows , the direction of magnetic force experienced by a current carrying wire in a perpendicular magnetic field and it is given by Fleming's left hand rule .
Arrow $$B$$ shows,the direction of magnetic field ,from north pole to south pole.
Arrow $$C$$ shows, the direction of conventional current from positive terminal to negative terminal of the battery.
Arrow $$D$$ shows, the direction of repulsion force exerted by wire in circuit $$X$$ to the wire of $$Y$$ due to fact that direction of current in both parallel wires is opposite.
Arrows $$E$$ shows ,the direction of magnetic field lines due to current carrying wire of circuit $$X$$ which is given by right hand thumb rule.
Choose the correct option which describe the magnetic field produced by a current in a long, straight wire?
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The field lines are radially inward to the wire
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The field increases in strength as the distance from the wire increases.
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The field lines are directed parallel to the wire, but opposite to the direction of the current
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The field lines are directed radially outward from the wire
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The field lines are concentric circles with the wire passing through the center
Explanation
The figure shows the nature of magnetic field lines due to a long, straight current-carrying wire.
It is evident that the field lines are concentric circles with the wire at the center.
The diagram below shows a wire carrying current towards the top off the page. A positively charged particle is shown moving directly toward the left side of the page at a particular instant.
What is the direction of the force on the positively charged particle at the instant shown, due to the magnetic field produced by the current in the wire?
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towards the top of the page
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towards the bottom of the page
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into the page
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out of the page
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towards the right side of the page
Explanation
The direction of magnetic field lines in the region left to the current carrying wire where the positive charge is moving will be perpendicularly inward the page according to the right thumb rule .
The direction of movement of positive charge can be taken the direction of current . As the positive charge is moving toward left therefore it will be the direction of current , and magnetic field is perpendicular inward the paper so according to Fleming's left hand rule , force on positive charge will be toward the bottom of the page .
Below a negatively charged particle is pictured moving north east through a magnetic field that points straight up. What is the direction of the force on the negatively charged particle at the moment it is pictured?
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northeast
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southeast
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southwest
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northwest
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up
Explanation
When we put our hand in such a way that index finger upward direction, middle finger is in south-west direction then our thumb is directed in north-west direction. Hence the direction of the force is in northwest direction.
A wire placed within a magnetic field has a current flowing in it as shown in the above figure. Identify the direction of the force exerted by the magnetic field on the wire.
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Point $$A$$
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Point $$B$$
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Point $$C$$
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Point $$D$$
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No forces are exerted on the wire
Explanation
The direction of magnetic force in a current-carrying wire in a magnetic field can be obtained by Fleming's left-hand rule. if we apply Fleming's left-hand rule in this wire the direction of the force will be in the vertically downward direction perpendicular to the magnetic field and the direction of the current.
Here, the forefinger of the left hand is pointed towards the right. The middle finger is pointed along the direction of the current. So, the thumb, indicating the direction of force, is pointed towards the point $$C$$.
The diagram below shows a positively charged particle moving toward the right and about to enter a magnetic field whose direction is shown by the blue arrows. What is the direction of the force on the positively charged particle (from our point of view) at the instant it enters the magnetic field?
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right
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left
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up
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toward us
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away from us
Explanation
Index finger represent the magnetic field which is downwards and the charge particle moving in right direction hence the current moving in left direction. Now we can predict the direction of the force by applying Fleming left hand rule which is away from us.
Which converts mechanical energy into electrical energy
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Motor
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Battery
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Generator
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Switch
Explanation
A generator is a device that converts motive power into electrical power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines, and even hand cranks.
Direction of induced EMF can be found from
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Lenz law
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Laplace law
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Fleming law
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None of the above
In above shown figure, the direction of magnetic force and magnetic field is given then find out the direction of the particle velocity, v.
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To the right
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Downward, in the plane of the page
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Upward, in the plane of the page
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Out of the plane of the page
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Into the plane of the page
Explanation
In the figure the direction of the magnetic field and force are given. Now if we apply Fleming left hand rule the direction of the particle velocity will be into the plane of the page.
An electron enters with a velocity $$v$$ to the right in a magnetic field $$B$$, also to the right. What direction is the force $$F$$ on the electron?
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An upward force
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A downward force
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A force to the left
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No force if felt
Explanation
According to the Fleming left hand rule, all the force, magnetic field and the velocity of the particle are mutually perpendicular to each other. As the field and the field are in the same plane so the particle will be not experiencing any force.
The diagram below shows a wire carrying conventional current in the direction shown by the red arrows.
The magnetic field is straight downward, as indicated by the blue X's.
What is the direction of the force exerted by the magnetic field on the wire?
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Upward
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Downward
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Northward
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Southward
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Westward
Explanation
The direction of force on a current carrying conductor placed normal to a magnetic field is given by Fleming's left hand rule , if we apply this rule for the given diagram , the direction of force will be downward.
The magnet is strongest near the
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Poles of the magnet
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Ends of the magnet
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Centre of the magnet
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One quarter point from the poles of the magnet
Explanation
A magnet is strongest near the poles at that point all the field lines are present and its density is maximum thus strongest.
A positive charge is at rest in a uniform magnetic field directed to the right.
What force does the positive charge feel, due to the magnetic field?
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An upward force.
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A downward force.
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A force to the left.
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No force is felt.
Explanation
For experiencing a magnetic force on a charge particle, the particle should move in the magnetic field with some velocity. As the velocity of the particle is zero so, the force on the particle is also zero.
A straight wire carries current toward the east.
What is the direction of the magnetic field directly below the wire?
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Northward
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Southward
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Eastward
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Westward
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Up
Explanation
According to the right hand thumb rule, if one
holds the wire carrying current in right hand
so that the thumb
points along the wire in the direction of the current, then the fingers will encircle the wire in the direction of the lines of magnetic force.
In this case, when thumb points towards east, the fingers curl to point towards north directly below the wire.
A straight wire carries conventional current toward the sky.
What is the direction of the magnetic field due to the current at a point west of the wire?
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North
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South
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East
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West
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Up
Explanation
Using Right-hand thumb rule, the direction of magnetic field due to a straight wire is shown in the figure above.
If we align our thumb in direction of current and curl our fingers anti-clockwise then at P out fingertips will point SOUTH.
Thus magnetic field at point P points in the south direction i.e option B is correct.
As a negatively charged bowling ball rolls eastward toward some bowling pins, in what direction does it experience a force, due to the earth's magnetic field (Assume the earth's field is pointing straight north)?
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North
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South
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East
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West
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Down
Explanation
According to the figure, $$\vec{v} = v\hat{y}$$ $$\vec{B} = -B\hat{x}$$
Charge of the ball $$Q = -q$$
$$\therefore$$ Magnetic force $$\vec{F} = -q(\vec{v}\times \vec{B}) = -q [v\hat{y} \times (-B)\hat{x}] = qvB (\hat{y} \times \hat{x}) =qvB $$ $$(-\hat{z})$$
Thus the ball experience a magnetic force in downward direction.
All of the following magnets pictured have magnetic field lines like the ones pictured in the diagram above. For which one are the poles correctly labeled?
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Explanation
The magnetic field lines originate at the North pole $$(N)$$ and terminate at the South pole
$$(S)$$
making closed loops.
Hence option B is correct.
An electron enters a magnetic field directed to the right, with a velocity toward the bottom of the screen.
What is the direction of the force on the electron?
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To the left
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Into the screen
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To the right
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Out of the screen
Explanation
It is given that the direction of the magnetic field is rightwards and the direction of the electron is from top to bottom of the screen hence the direction of the current is from bottom to top of the screen. Now by applying Fleming's left-hand rule, the direction of the force is directed into the screen.
The magnetic field lines due to a bar magnet correctly shown are:
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Explanation
As the magnetic field lines are closed curves.
Thus they must pass through the magnets as well and its direction is from south to north for same sense (direction)
Energy in a current - carrying coil is stored in the form of :
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Electric field
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Magnetic field
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Dielectric strength
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Heat
Explanation
Energy is actually stored in the magnetic field generated by the current flowing through the inductor
Which of the following figures depict non uniform magnetic field?
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Explanation
Uniform magnetic field has a bunch of symmetric lines of forces arranged in a regular fashion. So the correct option is D as lines of forces are not arranged in the regular fashion.
The magnetic lines of force due to a bar magnet are
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Curved lines
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Curved closed loops
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Concentric circles
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Parallel and straight
Explanation
The magnetic lines of force due to a bar magnet are closed loops. The field lines are directed from the north pole to the south pole outside the magnet.
The field lines are directed from the south pole to the north pole inside the magnet.
In alternating current:
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The direction of current is always positive
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The direction of current is always negative
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The direction of current changes constantly
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None of these
Explanation
A current that changes direction after equal intervals
of time is called an alternating current.
For the given distribution the magnetic field at point, $$P$$ is
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$$\dfrac{\mu _0}{4\pi}\bigodot$$
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$$\dfrac{\mu _0}{\pi}\bigotimes$$
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$$\dfrac{\mu _0}{2\pi}\bigotimes$$
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$$\dfrac{\mu _0}{2\pi}\bigodot$$
Explanation
$$\textbf{Step 1 - Formula of magnetic field due to infinite current carrying wire }$$
The magnetic field due to infinite straight wire is,
$$\vec {B} = \dfrac {\mu_{0} I}{2\pi d} \hat {n}$$ $$....(1)$$
According to write hand thumb rule, if thumb of right hand is
pointed towards the current then the direction of curl fingers
tells about the direction of magnetic field.
$$\textbf{Step 2 - Find net magnetic field at point P }$$
According to equation $$(1)$$ and right hand thumb rule,
the net magnetic field at $$P$$,
$$\vec {B} = \dfrac {\mu_{0} I_{1}}{2\pi d} (-\hat {n}) + \dfrac {\mu_{0}I_{2}}{2\pi d} (\hat {n})$$
Here $$\hat {n}$$ describe the outward direction,
$$\vec {B} = \dfrac {\mu_{0}}{2\pi} \left (\dfrac {-5}{2.5} + \dfrac {2.5}{2.5}\right ) \hat {n}$$
$$\vec {B} = \dfrac {\mu_{0}}{2\pi} \left (-\dfrac {2.5}{2.5} \right ) \hat {n}$$
$$\vec {B} = \dfrac {\mu_{0}}{2\pi} (-\hat {n})$$
or $$\vec {B} = \dfrac {\mu_{0}}{2\pi} \bigotimes$$
Hence option C correct.
Which of the following electrical devices works on the principle of electro-magnetic induction ?
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Electric fan
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Electric bulb
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Electric cooker
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L.E.D.
Explanation
Electric fan works on the principle of electro - magnetic induction. An electric fan works with the help of an electric motor the electric motor consists of a coil of wire wound around a metallic core. As electric current passes through the coil of wires, it produces rotational motion due to electro - magnetic induction.
Electromagnetic induction is not used in :
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Transformer
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Room heater
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AC generator
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Choke coil
Explanation
Room heater works on the principle of Joule's heating effect of current. It states that heat is produced in the conductor (or resistor) by passing an electric current through it for some time.
While transformer, AC generator, and choke coil, all work on the principle of Electromagnetic Induction.
Hence, the correct option is B
The phenomenon of producing an emf in a circuit whenever the magnetic flux linked with a coil changes is ................................
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Electro-magnetic induction
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Inducing current
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Inducing voltage
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Change in current
Explanation
The phenomenon of producing an emf in a circuit whenever the magnetic flux linked with a coil changes is electromagnetic induction. Electromagnetic induction is the production of an electromotive force (i.e., voltage) across an electrical conductor due to its dynamic interaction with a magnetic field. It has found many applications in technology, including electrical components such as inductors and transformers, and devices such as electric motors and generators.
Electromagnetic induction is not used in
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Transformer
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Room heater
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AC generator
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Choke coil
Explanation
Room heater works on the principle of Joule's heating effect of current that heat is produced in the conductor (or resistor) on passing an electric current through it for some time.
While transformer, AC generator, and choke coil work on the principle of Electromagnetic induction.
A beam of protons is moving horizontally towards you. As it approaches you, it passes through a magnetic field which is directed upwards. As you see it, the magnetic field will deflect the beam to the:
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Right
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Left
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Top
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Bottom
Explanation
Using Fleming's Left-hand rule as shown in the attached figure, the net force acting on the protons beam experiences a force to the left. Hence, the magnetic field deflects the beam to the left.
Which one of the following statements best describes the nature of the field lines due to a bar magnet?
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Field lines start from the north pole and end on the south pole. Any number of field lines can pass through a point
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Field lines start from the north pole and end on the south pole. Only one field line passes through a point
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Field lines are continuous lines passing inside and outside the magnet. Only one field line passes through a point
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Field lines are continuous lines passing inside and outside the magnet. Any number of field lines can pass through a point
Explanation
The properties of magnetic filed lines are that they start from north pole and end at south pole (outside the magnet). But they flow from south to north pole inside the magnet forming a continuous closed loop. They are very near to each other where the magnetic field is strong whereas they are far away from each other where magnetic field is weak. At poles, magnetic field is the strongest. Thus the magnetic lines of forces are the nearest at the poles. No two magnetic line of forces intersect with each other.
Thus correct answer is option C.
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