Magnetic Effect, Magnetism and EMI, Class 12 Physics MCQ Quiz Test

MCQ 1:
Magnetic lines are -

continuous
discontinuous
sometimes continuous and sometimes discontinuous
nothing can be said

MCQ 2:
A tiny loop of current behaves as a magnetic dipole -

true
false
may be true or false
nothing can be said

MCQ 3:
The horizontal component of earth’s magnetic field at any place is 0.36 × 10^–4 Weber/m². If the angle of dip at that place is 60º then the value of vertical component of earth’s magnetic field will be (in Wb/m²) -

0.12 × 10^-4
0.24 × 10^-4
0.40 × 10^-4
0.62 × 10^-4

MCQ 4:
The value of angle of dip at a place on earth is 45º. If the horizontal component of earth’s magnetic field is 5 × 10^-5 Tesla then the total magnetic of earth’s magnetic field of earth will be -

5 √2 × 10^-5 Tesla
10 √2 × 10^-5 Tesla
15 √2 × 10^-5 Tesla
zero

MCQ 5:
At a certain place, horizontal component is √3 times the vertical component. The angle of dip of this place is -

0
π/3
π/6
none of these

MCQ 6:
A steel wire of length λ has a magnetic moment M. It is then bent into a semicircular arc. The new magnetic moment is -

M
2 M/π
M/λ
M ∝ λ

MCQ 7:
Earth’s magnetic field always has a horizontal component except at -

equator
magnetic pole
a latitude of 60°
an inclination of 60°

MCQ 8:
If a uniform wire loop is connected to the terminals of a battery then the magnetic induction at the centre will be -

inversely proportional to the radius of the loop
infinite
directly proportional to applied e.m.f.
Zero

MCQ 9:
An electric current is flowing in a very long pin as shown in the figure. The value of magnetic flux density at point O will be -

MCQ 10:
A current i is flowing in a conductor shaped as shown in the figure. The radius of curved part is r and length of straight portions is very large. The value of magnetic field at the centre will be -

MCQ 11:
An electric current of i ampere is flowing in a long conductor as shown in the figure. The magnitude and direction of magnetic induction at the centre of circular part will be -

Zero

MCQ 12:
You are given a closed circuit with radii a and b as shown in fig carrying current i. The magnetic dipole moment of the circuit is -

π (a² + b²) i
1/2 π (a² + b²) i
π (a² - b²) i
1/2 π (a² - b²) i

MCQ 13:
An α particle is moving in a magnetic field of (3i + 2j) tesla with a velocity of 5×10⁵ m/s. The magnetic force acting on the particle will be -

3.2 × 10^–13 dyne
3.2 × 10¹³ N
0
3.2 × 10^–13 N

MCQ 14:
A straight horizontal stretch of copper wire carries a current i = 30 A. The linear mass density of the wire is 45 g/m. What is the magnitude of the magnetic field needed to "float" the wire, that is to be balance its weight?

147 G
441 G
14.7 G
0 G

MCQ 15:
An electric current of 30 ampere is flowing in each of two parallel conducting wires places 5 cm apart. The force acting per unit length on either of the wires will be -

3.6 × 10^–3 N/m
3.6 × 10^–3 Dyne/cm
3.6 × 10^–5 N/m
3.6 × 10^–2 N/m

MCQ 16:
The length of a solenoid is 0.4 m and the number turns in it is 500. A current of 3 amp, is flowing in it. In a small coil of radius 0.01 m and number of turns 10, a current of 0.4 amp. is flowing. The torque necessary tp keep the axis of this coil perpendicular to the axis of solenoid will be -

5.92 × 10^–6 N-m
5.92 × 10^–4 N-m
5.92 × 10^–6 Dyne-cm
5.92 × 10^–5 Dyne-cm

MCQ 17:
If the current in the primary coil is reduced from 3.0 ampere to zero in 0.001 second, the induced e.m.f in the secondary coil is 1500 volt. The mutual inductance of the two coils will be-

0.5 H
0.05 H
0.005 H
0.0005 H

MCQ 18:
A small coil of N₁ turns, l₁ length, is tightly wound over the centre of a long solenoid of length l₂, area of cross-section A and number of turns N₂. If a current I flows in the small coil, Then what is the flux through the long, solenoid -

Zero

infinite

MCQ 19:
The current flowing in a coil whose coefficient of self-induction is 0.4 mH changes by 250 mA in 0.1 sec. The electromotive force (e.m.f.) induced in the coil will be-

100 mv
30 mv
.01 mv
1 mv

MCQ 20:
A 10-meter wire is kept in east-west direction. It is falling down with a speed of 5.0 meter/second, perpendicular to the horizontal component of earth's magnetic field of 0.30 × 10^–4 weber/meter². The momentary potential difference induced between the ends of the wire will be-

0.0015 V
0.015 V
0.15 V
1.5 V

MCQ 21:
A copper disc of radius 0.1 m rotates about its centre with 10 revolutions per second in 'a uniform magnetic field of 0.1 tesla. The emf induced across the radius of the disc is-

π/10 V
2π/10 V
10π mV
20π mV

MCQ 22:
Two rail tracks, insulated from each other and the ground, are connected to millivoltmeter. What is the reading of the milli voltmeter when a train passes at a speed of 180 km/hr along the track, given that the vertical component of earth's magnetic field is 0.2 × 10^–4 Wb/m² and rails are separated by 1 meter.

1 mV
10 mV
100 mV
1 V

MCQ 23:
The annular disc of copper, with inner radius a and outer radius b is rotating with a uniform angular speed ω, in a region where a uniform magnetic field B along the axis of rotation exists. Then, the emf induced between inner side and the outer rim of the disc is -

Zero
1/2 Bω a²
1/2 Bω b²
1/2 Bω(b² – a²)

MCQ 24:
A loop of wire is placed in a magnetic field B = 0.02 i tesla. Then the flux through the loop is its area vector is A = 30 i + 16j + 23 k cm², is

60μ W
32μ Wb
46μ Wb
138μ Wb

MCQ 25:
The magnetic flux passing perpendicular to the plane of the coil and directed into the paper is varying according to the relation. φ = 3t² + 2t + 3, Where φ is in milliwebers and t is in seconds. Then the magnitude of emf induced in the loop when t = 2 second is -

31 mV
19 mV
14 mV
6 mV