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Physics M.C.Q (1 Marks)

Magnetism · CBSE STD 12 Science (CBSE - English Medium). 303 questions.

Questions · Page 6 of 7

M.C.Q (1 Marks)

MCQ 2511 Mark
A magnet when placed perpendicular to a uniform field of strength $10^{-4} \mathrm{~Wb} / \mathrm{m}^2$ experiences a maximum couple of moment $4 \times 10^{-5} \mathrm{~N} / \mathrm{m}$. What is its magnetic momen
  • ✓
    $0.4\ \mathrm{A} \times \mathrm{m}^2$
  • B
    $0.2\  \mathrm{A} \times \mathrm{m}^2$
  • C
    $0.6\ \mathrm{A} \times \mathrm{m}^2$
  • D
    $0.04\  \mathrm{A} \times \mathrm{m}^2$
Answer
Correct option: A.
$0.4\ \mathrm{A} \times \mathrm{m}^2$
(a) $0.4\ \mathrm{A} \times \mathrm{m}^2$
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MCQ 2521 Mark
A current loop placed in a magnetic field behaves like a
  • ✓
    Magnetic dipole
  • B
    Magnetic substance
  • C
    Magnetic pole
  • D
    All are true
Answer
Correct option: A.
Magnetic dipole
 Magnetic dipole
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MCQ 2531 Mark
The magnet can be completely demagnetized by
  • A
    Breaking the magnet into small pieces
  • B
    Heating it slightly
  • C
    Droping it into ice cold water
  • ✓
    A reverse field of appropriate strength
Answer
Correct option: D.
A reverse field of appropriate strength
 A reverse field of appropriate strength
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MCQ 2541 Mark
If a piece of metal was thought to be magnet, which one of the following observations would offer conclusive evidence
  • A
    It attracts a known magnet
  • ✓
    It repels a known magnet
  • C
    Neither (a) nor (b)
  • D
    It attracts a steel screw driver
Answer
Correct option: B.
It repels a known magnet
 It repels a known magnet
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MCQ 2551 Mark
For protecting a sensitive equipment from the external magnetic field, it should be
  • A
    Placed inside an aluminium cane
  • ✓
    Placed inside an iron cane
  • C
    Wrapped with insulation around it when passing current through it
  • D
    Surrounded with fine copper sheet
Answer
Correct option: B.
Placed inside an iron cane
 Placed inside an iron cane
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MCQ 2571 Mark
A bar magnet of magnetic moment $\vec M$ is placed in a magnetic field of induction $\vec B$. The torque exerted on it is
  • A
    $\vec M.\vec B$
  • B
    $-\vec M.\vec B$
  • ✓
    $\vec M \times \vec B$
  • D
    $\vec B \times \vec M$
Answer
Correct option: C.
$\vec M \times \vec B$
(c) $\vec M \times \vec B$
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MCQ 2581 Mark
A straight wire carrying current i is turned into a circular loop. If the magnitude of magnetic moment associated with it in M.K.S. unit is M, the length of wire will be
  • A
    4πiM
  • ✓
    $\sqrt{\frac{4 \pi M}{i}}$
  • C
    $\sqrt{\frac{4 \pi i}{M}}$
  • D
    $\frac{M n}{4 \mathrm{i}}$
Answer
Correct option: B.
$\sqrt{\frac{4 \pi M}{i}}$
(b) $\sqrt{\frac{4 \pi M}{i}}$
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MCQ 2591 Mark
The incorrect statement regarding the lines of force of the magnetic field B is
  • A
    Magnetic intensity is a measure of lines of force passing through unit area held normal to it
  • B
    Magnetic lines of force form a close curve
  • ✓
    Inside a magnet, its magnetic lines of force move from north pole of a magnet towards its south pole
  • D
    Due to a magnet magnetic lines of force never cut each other
Answer
Correct option: C.
Inside a magnet, its magnetic lines of force move from north pole of a magnet towards its south pole
 Inside a magnet, its magnetic lines of force move from north pole of a magnet towards its south pole
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MCQ 2601 Mark
The magnetic field to a small magnetic dipole of magnetic moment M, at distance r from the centre on the equatorial line is given by (in M.K.S. system)
  • A
    $\frac{\mu_0}{4 \pi} \times \frac{M}{r^2}$
  • ✓
    $\frac{\mu_0}{4 \pi} \times \frac{M}{r^3}$
  • C
    $\frac{\mu_0}{4 \pi} \times \frac{2 M}{r^2}$
  • D
    $\frac{\mu_0}{4 \pi} \times \frac{2 M}{r^3}$
Answer
Correct option: B.
$\frac{\mu_0}{4 \pi} \times \frac{M}{r^3}$
(b) $\frac{\mu_0}{4 \pi} \times \frac{M}{r^3}$
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MCQ 2611 Mark
A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.16 Tesla experiences a torque of magnitude 0.032 Joule. The magnetic moment of the bar magnet will be
  • A
    0.23 Joule/Tesla
  • ✓
    0.40 Joule/Tesla
  • C
    0.80Joule/Tesla
  • D
    Zero
Answer
Correct option: B.
0.40 Joule/Tesla
 0.40 Joule/Tesla
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MCQ 2621 Mark
The S.I. unit of magnetic permeability is 
  • A
    $\mathrm{Am}^{-1}$
  • B
    Am
  • ✓
    Henry $\mathrm{m}^{-1}$
  • D
    No unit, it is a dimensionless number
Answer
Correct option: C.
Henry $\mathrm{m}^{-1}$
(c) Henry $\mathrm{m}^{-1}$
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MCQ 2631 Mark
A permanent magnet
  • A
    Attracts all substances
  • ✓
    Attracts only magnetic substances
  • C
    Attracts magnetic substances and repels all non-magnetic substances
  • D
    Attracts non-magnetic substances and repels magnetic substances
Answer
Correct option: B.
Attracts only magnetic substances
 Attracts only magnetic substances
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MCQ 2641 Mark
The unit of magnetic moment is
  • A
    Wb/m
  • B
    Wb.$\mathrm{m}^2$
  • C
    A.m
  • ✓
    A. $\mathrm{m}^2$
Answer
Correct option: D.
A. $\mathrm{m}^2$
(d) A. $\mathrm{m}^2$
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MCQ 2651 Mark
Magnetic lines of force due to a bar magnet do not intersect because
  • ✓
    A point always has a single net magnetic field
  • B
    The lines have similar charges and so repel each other
  • C
    The lines always diverge from a single point
  • D
    The lines need magnetic lenses to be made to intersect
Answer
Correct option: A.
A point always has a single net magnetic field
  A point always has a single net magnetic field
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MCQ 2661 Mark
A bar magnet of magnetic moment $10^4 \mathrm{~J} / \mathrm{T}$ is free to rotate in a horizontal plane. The work done in rotating the magnet slowly from a direction parallel to a horizontal magnetic field of $4 \times 10^{-5} \mathrm{~T}$ to a direction 60$^\circ$ from the field will be
  • ✓
    0.2 J
  • B
    2.0 J
  • C
    4.18 J
  • D
    $2 × 10^2$ J
Answer
Correct option: A.
0.2 J
(a) 0.2 J
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MCQ 2671 Mark
Force between two identical bar magnets whose centres are r metre apart is 4.8 N, when their axes are in the same line. If separation is increased to 2r, the force between them is reduced to
  • A
    2.4N
  • B
    1.2N
  • C
    0.6N
  • ✓
    0.3N
Answer
Correct option: D.
0.3N
 0.3N
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MCQ 2681 Mark
The work done in turning a magnet of magnetic moment 'M' by an angle of 90° from the meridian is 'n' times the corresponding work done to turn it through an angle of 60°, where 'n' is given by
  • A
    1/2
  • ✓
    2
  • C
    1/4
  • D
    1
Answer
Correct option: B.
2
 2
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MCQ 2691 Mark
A sensitive magnetic instrument can be shielded very effectively from outside magnetic fields by placing it inside a box of
  • A
    Teak wood
  • B
    Plastic material
  • ✓
    Soft iron of high permeability
  • D
    A metal of high conductivity
Answer
Correct option: C.
Soft iron of high permeability
 Soft iron of high permeability
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MCQ 2701 Mark
A small bar magnet of moment M is placed in a uniform field H. If magnet makes an angle of 30° with field, the torque acting on the magnet is
  • A
    $\mathrm{MH}$
  • ✓
    $\frac{\mathrm{MH}}{2}$
  • C
    $\frac{\mathrm{MH}}{3}$
  • D
    $\frac{\mathrm{MH}}{4}$
Answer
Correct option: B.
$\frac{\mathrm{MH}}{2}$
(b) $\frac{\mathrm{MH}}{2}$
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MCQ 2711 Mark
Force between two unit pole strength placed at a distance of one metre is
  • A
    1 N
  • B
    $\frac{10^{-7}}{4 \pi} \mathrm{N}$
  • ✓
    $10^{-7} \mathrm{~N}$
  • D
    $4 \pi \times 10^{-7} \mathrm{~N}$
Answer
Correct option: C.
$10^{-7} \mathrm{~N}$
(c) $10^{-7} \mathrm{~N}$
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MCQ 2721 Mark
What happens to the force between magnetic poles when their pole strength and the distance between them are both doubled
  • A
    Force increases to two times the previous value
  • ✓
    No change
  • C
    Force decreases to half the previous value
  • D
    Force increases to four times the previous value
Answer
Correct option: B.
No change
 No change
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MCQ 2731 Mark
Magnetic induction is a
  • A
    Scalar quantity
  • ✓
    Vector quantity
  • C
    Both (a) and (b)
  • D
    None of the above
Answer
Correct option: B.
Vector quantity
Vector quantity
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MCQ 2741 Mark
Two identical thin bar magnets each of length l and pole strength m are placed at right angle to each other with north pole of one touching south pole of the other. Magnetic moment of the system is
  • A
    ml
  • B
    2ml
  • ✓
    $\sqrt{2} \mathrm{ml}$
  • D
    $\frac{1}{2} \mathrm{ml}$
Answer
Correct option: C.
$\sqrt{2} \mathrm{ml}$
(c) $\sqrt{2} \mathrm{ml}$
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MCQ 2751 Mark
A long magnetic needle of length 2L, magnetic moment M and pole strength m units is broken into two pieces at the middle. The magnetic moment and pole strength of each piece will be
  • A
    $\frac{M}{2},\frac{m}{2}$
  • B
    $M,\frac{m}{2}$
  • ✓
    $\frac{M}{2},m$
  • D
    M, m
Answer
Correct option: C.
$\frac{M}{2},m$
(c) $\frac{M}{2},m$
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MCQ 2761 Mark
A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60°. The torque required to maintain the needle in this position will be
  • ✓
    $\sqrt 3  W$
  • B
    W
  • C
    $\frac{\sqrt 3}{2}W$
  • D
    2W
Answer
Correct option: A.
$\sqrt 3  W$
(a) $\sqrt 3  W$
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MCQ 2771 Mark
The magnetic induction in air at a distance d from an isolated point pole of strength m unit will be
  • A
    $\frac{m}{d}$
  • ✓
    $\frac{m}{d^2}$
  • C
    md
  • D
    $md^2$
Answer
Correct option: B.
$\frac{m}{d^2}$
(b) $\frac{m}{d^2}$
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MCQ 2781 Mark
If the magnetic flux is expressed in weber, then magnetic induction can be expressed in
  • ✓
    Weber/m$^2$
  • B
    Weber/m
  • C
    Weber$-$m
  • D
    Weber$-$m$^2$
Answer
Correct option: A.
Weber/m$^2$
Weber/m$^2$
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MCQ 2791 Mark
Magnetic field intensity is defined as
  • A
    Magnetic moment per unit volume
  • ✓
    Magnetic induction force acting on a unit magnetic pole
  • C
    Number of lines of force crossing per unit area
  • D
    Number of lines of force crossing per unit volume
Answer
Correct option: B.
Magnetic induction force acting on a unit magnetic pole
 Magnetic induction force acting on a unit magnetic pole
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MCQ 2801 Mark
A bar magnet of length 10 cm and having the pole strength equal to $10^{-3}$ weber is kept in a magnetic field having magnetic induction (B) equal to $4 \pi \times 10^{-3}$ Tesla. It makes an angle of 30$^\circ$ with the direction of magnetic induction. The value of the torque acting on the magnet is
$\left(\mu_0=4 \pi \times 10^{-7}\right.$ weber/amp $\left.\times \mathrm{m}\right)$
  • ✓
    $2 \pi \times 10^{-7} \mathrm{~N} \times \mathrm{m}$
  • B
    $2 \pi \times 10^{-5} \mathrm{~N} \times \mathrm{m}$
  • C
    $0.5 \mathrm{~N} \times \mathrm{m}$
  • D
    $0.5 \times 10^2 \mathrm{~N} \times{\mathrm{m}}$
Answer
Correct option: A.
$2 \pi \times 10^{-7} \mathrm{~N} \times \mathrm{m}$
(a) $2 \pi \times 10^{-7} \mathrm{~N} \times \mathrm{m}$
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MCQ 2811 Mark
A long magnet is cut in two parts in such a way that the ratio of their lengths is 2 : 1. The ratio of pole strengths of both the section is
  • ✓
    Equal
  • B
    In the ratio of 2 : 1
  • C
    In the ratio of 1 : 2
  • D
    In the ratio of 4 : 1
Answer
Correct option: A.
Equal
Equal
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MCQ 2821 Mark
Two small bar magnets are placed in a line with like poles facing each other at a certain distance d apart. If the length of each magnet is negligible as compared to d, the force between them will be inversely proportional to
  • A
    d
  • B
    $\mathrm{d}^2$
  • C
    $\frac{1}{\mathrm{~d}^2}$
  • ✓
    $\mathrm{d}^4$
Answer
Correct option: D.
$\mathrm{d}^4$
(d) $\mathrm{d}^4$
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MCQ 2831 Mark
If a bar magnet of magnetic moment M is freely suspended in a uniform magnetic field of strength B, the work done in rotating the magnet through an angle θ is
  • A
    MB(1- sinθ)
  • B
    MB sinθ
  • C
    MB cosθ
  • ✓
    MB(1 – cosθ)
Answer
Correct option: D.
MB(1 – cosθ)
 MB(1 – cosθ)
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MCQ 2841 Mark
Two short magnets with their axes horizontal and perpendicular to the magnetic meridian are placed with their centres 40 cm east and 50 cm west of magnetic needle. If the needle remains undeflected, the ratio of their magnetic moments $M_1: M_2$ is 
  • A
    4 : 5
  • B
    16 : 25
  • ✓
    64 : 125
  • D
    $2: \sqrt{5}$
Answer
Correct option: C.
64 : 125
(c) 64 : 125
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MCQ 2851 Mark
Points A and B are situated perpendicular to the axis of a 2cm long bar magnet at large distances X and 3X from its centre on opposite sides. The ratio of the magnetic fields at A and B will be approximately equal to
  • A
    1 : 9
  • B
    2 : 9
  • ✓
    27 : 1
  • D
    9 : 1
Answer
Correct option: C.
27 : 1
27 : 1
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MCQ 2861 Mark
The figure below shows the north and south poles of a permanent magnet in which n turn coil of area of cross-section A is resting, such that for a current i passed through the coil, the plane of the coil makes an angle θ with respect to the direction of magnetic field B. If the plane of the magnetic field and the coil are horizontal and vertical respectively, the torque on the coil will be
  • ✓
    τ = niAB cosθ
  • B
    τ = niAB sinθ
  • C
    τ = niAB
  • D
    None of the above, since the magnetic field is radial
Answer
Correct option: A.
τ = niAB cosθ
(a) τ = niAB cosθ
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MCQ 2871 Mark
The field due to a magnet at a distance R from the centre of the magnet is proportional to
  • A
    $R^2$
  • B
    $R^3$
  • C
    $1 / R^2$
  • ✓
    $1 / R^3$
Answer
Correct option: D.
$1 / R^3$
(d) $1 / R^3$
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MCQ 2881 Mark
In the case of bar magnet, lines of magnetic induction
  • A
    Start from the north pole and end at the south pole
  • ✓
    Run continuously through the bar and outside
  • C
    Emerge in circular paths from the middle of the bar
  • D
    Are produced only at the north pole like rays of light from a bulb
Answer
Correct option: B.
Run continuously through the bar and outside
Run continuously through the bar and outside
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MCQ 2891 Mark
Which of the following, the most suitable material for making permanent magnet is
  • ✓
    Steel
  • B
    Soft iron
  • C
    Copper
  • D
    Nickel
Answer
Correct option: A.
Steel
 Steel
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MCQ 2901 Mark
The magnetic field due to a short magnet at a point on its axis at distance X cm from the middle point of the magnet is 200 Gauss. The magnetic field at a point on the neutral axis at a distance X cm from the middle of the magnet is
  • ✓
    100 Gauss
  • B
    400 Gauss
  • C
    50 Gauss
  • D
    200 Gauss
Answer
Correct option: A.
100 Gauss
100 Gauss
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MCQ 2911 Mark
A bar magnet having centre $O$ has a length of 4 cm . Point $P_1$ is in the broad side-on and $P_2$ is in the end side-on position with $\mathrm{OP}_1=\mathrm{OP}_2=10$ metres. The ratio of magnetic intensities H at $\mathrm{P}_1$ and $\mathrm{P}_2$ is
  • A
    $\mathrm{H}_1: \mathrm{H}_2=16: 100$
  • ✓
    $\mathrm{H}_1: \mathrm{H}_2=1: 2$
  • C
    $\mathrm{H}_1: \mathrm{H}_2=2: 1$
  • D
    $\mathrm{H}_1: \mathrm{H}_2=100: 16$
Answer
Correct option: B.
$\mathrm{H}_1: \mathrm{H}_2=1: 2$
(b) $\mathrm{H}_1: \mathrm{H}_2=1: 2$
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MCQ 2921 Mark
A magnet of magnetic moment 20 C.G.S. units is freely suspended in a uniform magnetic field of intensity 0.3 C.G.S. units. The amount of work done in deflecting it by an angle of $30^{\circ}$ in C.G.S. units is
  • A
    6
  • B
    $3\sqrt 3$
  • ✓
    $3(2-\sqrt 3)$
  • D
    3
Answer
Correct option: C.
$3(2-\sqrt 3)$
(c) $3(2-\sqrt 3)$
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MCQ 2931 Mark
The magnetic field at a point x on the axis of a small bar magnet is equal to the field at a point y on the equator of the same magnet. The ratio of the distances of x and y from the centre of the magnet is
  • A
    $2^{-3}$
  • B
    $2^{-1/3}$
  • C
    $2^3$
  • ✓
    $2^{1/3}$
Answer
Correct option: D.
$2^{1/3}$
(d) $2^{1/3}$
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MCQ 2941 Mark
The pole strength of a bar magnet is $48$ ampere$-$metre and the distance between its poles is $25 \ cm$. The moment of the couple by which it can be placed at an angle of $30^\circ$ with the uniform magnetic intensity of flux density $0.15$ Newton /ampere$-$metre will be
  • A
    $12$ Newton $\times$ metre
  • B
    $18$ Newton $\times$ metre
  • ✓
    $0.9$ Newton $\times$ metre
  • D
    None of the above
Answer
Correct option: C.
$0.9$ Newton $\times$ metre
$0.9$ Newton $\times$ metre
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MCQ 2951 Mark
Unit of magnetic flux density $($or magnetic induction$)$ is
  • A
    Tesla
  • B
    Weber/metre$^2$
  • C
    Newton/ampere$-$metre
  • ✓
    All of the above
Answer
Correct option: D.
All of the above
All of the above
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MCQ 2961 Mark
Magnetic intensity for an axial point due to a short bar magnet of magnetic moment M is given by
  • A
    $\frac{\mu_0}{4 \pi} {\times} \frac{M}{d^3}$
  • B
    $\frac{\mu_0}{4 \pi} \times \frac{M}{d}^2$
  • ✓
    $\frac{\mu_0}{2 \pi} \times \frac{M}{d^3}$
  • D
    $\frac{\mu_0}{2 \pi} \times \frac{M}{d^2}$
Answer
Correct option: C.
$\frac{\mu_0}{2 \pi} \times \frac{M}{d^3}$
(c) $\frac{\mu_0}{2 \pi} \times \frac{M}{d^3}$
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MCQ 2971 Mark
A magnet is placed in iron powder and then taken out, then maximum iron powder is at
  • A
    Some away from north pole
  • B
    Some away from south pole
  • C
    The middle of the magnet
  • ✓
    The end of the magnet
Answer
Correct option: D.
The end of the magnet
The end of the magnet
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MCQ 2981 Mark
A magnet of magnetic moment M and pole strength m is divided in two equal parts, then magnetic moment of each part will be
  • A
    M
  • ✓
    M/2
  • C
    M/4
  • D
    2M
Answer
Correct option: B.
M/2
M/2
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MCQ 2991 Mark
Points A and B are situated along the extended axis of 2 cm long bar magnet at a distance x and 2x cm respectively. From the pole nearer to the points, the ratio of the magnetic field at A and B will be
  • A
    4 : 1 exactly
  • B
    4 : 1 approx.
  • C
    8 : 1 exactly
  • ✓
    8 : 1 approx.
Answer
Correct option: D.
8 : 1 approx.
8 : 1 approx.
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MCQ 3001 Mark
If a magnet of pole strength m is divided into four parts such that the length and width of each part is half that of initial one, then the pole strength of each part will be
  • A
    m/4
  • ✓
    m/2
  • C
    m/8
  • D
    4m
Answer
Correct option: B.
m/2
m/2
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