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Science M.C.Q

Magnetic Effects of Electric Current · MP Board (MPBSE) STD 10 (Madhya Pradesh - English Medium). 12 questions.

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M.C.Q

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12 questions · timed · auto-graded

MCQ 11 Mark
The most important safety method used for protecting home appliances from short circuiting or overloading is:
  • A
    Earthing.
  • ✓
    Use of fuse.
  • C
    Use of stabilizers.
  • D
    Use of electric meter.
Answer
Correct option: B.
Use of fuse.
Use of electric fuse is the most important method used for protecting home appliances from short circuiting or overloading.
Generally, thin wire with low melting having specific rating is connected in series with the electric devices. When the current passing through the fuse exceeds a specific value then by heating effect of current it melts and breaks the circuit.
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MCQ 21 Mark
Choose the incorrect statement from the following regarding magnetic lines of field:
  • A
    The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points.
  • B
    Magnetic field lines are closed curves.
  • ✓
    If magnetic field lines are parallel and equidistant, they represent zero field strength.
  • D
    Relative strength of magnetic field is shown by the degree of closeness of the field lines.
Answer
Correct option: C.
If magnetic field lines are parallel and equidistant, they represent zero field strength.
Magnetic field lines appear parallel when they are far from the magnet. But this does not mean that field strength is zero. No field line would be present where field strength becomes zero.
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MCQ 31 Mark
For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is:
  • A
    The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.
  • B
    The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.
  • ✓
    The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
  • D
    The N- and S-poles exchange position when the direction of current through the solenoid is reversed.
Answer
Correct option: C.
The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
A solenoid behaves like a bar magnet. Hence, the pattern of the magnetic field associated with the solenoid is same as the pattern of the magnetic field around a bar magnet.
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MCQ 41 Mark
Choose the incorrect statement:
  • A
    Fleming’s right-hand rule is a simple rule to know the direction of induced current.
  • B
    The right-hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors.
  • C
    The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically.
  • ✓
    In India, the AC changes direction after every $\frac{1}{50}$ second.
Answer
Correct option: D.
In India, the AC changes direction after every $\frac{1}{50}$ second.
Frequency of AC in India = 50Hz
$\therefore$ AC completes 1 cycle in $\frac{1}{50}$ seconds.

In one cycle, AC changes direction two times. Hence, time after which AC changes direction,

$=\frac{1}{2\times50}=\frac{1}{100}\text{ second}.$
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MCQ 51 Mark
To convert an AC generator into DC generator:
  • ✓
    Split-ring type commutator must be used.
  • B
    Slip rings and brushes must be used.
  • C
    A stronger magnetic field has to be used.
  • D
    A rectangular wire loop has to be used.
Answer
Correct option: A.
Split-ring type commutator must be used.
AC generator has slip rings while the DC generator has a split ring type commutator. To convert an AC generator into DC generator the split ring type commutator with which unidirectional current is obtained.
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MCQ 61 Mark
Commercial electric motors do not use:
  • A
    An electromagnet to rotate the armature.
  • B
    Effectively large number of turns of conducting wire in the current carrying coil.
  • ✓
    A permanent magnet to rotate the armature.
  • D
    A soft iron core on which the coil is wound.
Answer
Correct option: C.
A permanent magnet to rotate the armature.
 Electromagnet is used instead of permanent magnet in commercial electric motor.
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MCQ 71 Mark

If the key in the arrangement (Figure) is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are:
  • A
    Concentric circles.
  • B
    Eliptical in shape.
  • ✓
    Straight lines parallel to each other.
  • D
    Concentric circles near the point O but of elliptical shapes as we go away from it.
Answer
Correct option: C.
Straight lines parallel to each other.
If key is taken out then current will stop and no magnetic field exists due to the conductor. Therefore at the point O, there will be earth’s magnetic field and they will be straight lines parallel to each other.
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MCQ 81 Mark
The strength of magnetic field inside a long current carrying straight solenoid is:
  • A
    More at the ends than at the centre.
  • B
    Minimum in the middle.
  • ✓
    Same at all points.
  • D
    Found to increase from one end to the other.
Answer
Correct option: C.
Same at all points.
Magnetic field inside a long current carrying straight solenoid is uniform.
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MCQ 91 Mark

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in Figure. In the field an electron and a proton move as shown. The electron and the proton experience:
  • ✓
    Forces both pointing into the plane of paper.
  • B
    Forces both pointing out of the plane of paper.
  • C
    Forces pointing into the plane of paper and out of the plane of paper, respectively.
  • D
    Force pointing opposite and along the direction of the uniform magnetic field respectively.
Answer
Correct option: A.
Forces both pointing into the plane of paper.
Apply Fleming’s left hand rule and considering the flow of current in the direction of the movement of proton and in the direction opposite to the movement of electron.
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MCQ 101 Mark
In the arrangement shown in Figure there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then,
  • A
    The deflection in the galvanometer remains zero throughout.
  • B
    There is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed.
  • C
    There are momentary galvanometer deflections that die out shortly; the deflections are in the same direction.
  • ✓
    There are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions.
Answer
Correct option: D.
There are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions.
When key is plugged, galvanometer shows momentary deflection in one direction. When the key is removed, galvanometer shows momentary deflection in opposite direction.
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MCQ 111 Mark
A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in Figure. The direction of magnetic field at a point will be North to South:
  • A
    Directly above the wire.
  • ✓
    Directly below the wire.
  • C
    At a point located in the plane of the paper, on the north side of the wire.
  • D
    At a point located in the plane of the paper, on the south side of the wire.
Answer
Correct option: B.
Directly below the wire.
 If we observe the direction of magnetic field by applying right hand thumb rule then, we will find that the direction of magnetic field is from North to South below the wire.
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MCQ 121 Mark

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to:
  • ✓
    A.
  • B
    B.
  • C
    A if the current is small, and B if the current is large.
  • D
    B if the current is small and A if the current is large.
Answer
Correct option: A.
A.
 If current seems to flow in anticlockwise direction in a coil, then that face of the coil acts as N-pole.
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