Question Bank for 12th Class Physics Electro Magnetic Induction MCQs - Electromagnetic Induction

1)

A square of side L meters lies in the x-y plane in a region where the magnetic field is given by \[\operatorname{B}={{B}_{0}}\text{ (}2\hat{i}+3\hat{j}+4\hat{k})\] Testa, where \[{{B}_{0}}\] is constant. The magnitude of flux passing through the square is

A)

\[2{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\]

B)

\[3{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\]

C)

\[4{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\]

D)

\[\sqrt{29}{{B}_{0}}{{\text{L}}^{2}}\text{Wb}\]

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2)

A loop, made of straight edges has six corners at A (0, 0, 0), B (L, 0, 0) C (L, L, 0), D (0, L,0), E (0, L, L) and F (0,0, L). A magnetic field B= \[{{B}_{0}}\text{ }(\hat{i}+\hat{k})\] Testa is present in the region. The flux passing through the loop ABCDEFA (in that order) is

A)

\[{{B}_{0}}{{L}^{2}}Wb\].

B)

2\[{{B}_{0}}{{L}^{2}}Wb\].

C)

\[\sqrt{2}{{B}_{0}}{{L}^{2}}Wb\].

D)

\[4{{B}_{0}}{{L}^{2}}Wb\] .

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3)

A cylindrical bar magnet is rotated about its axis in the figure. A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then

A)

a direct current flows in the ammeter A.

B)

no current flows through the ammeter A.

C)

an alternating sinusoidal current flows through the ammeter A with a time period \[2\pi /\omega \]

D)

a time varying non-sinusoidal current flows through the ammeter A.

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4)

There are two coils A and B as shown in figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counter clockwise. B is kept stationary when A moves. We can infer that

A)

there is a constant current in the clockwise direction in A.

B)

there is a varying current in A.

C)

there is no current in A.

D)

there is a constant current in the counter clockwise direction in A.

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5)

Same as problem 4 except the coil A is made to rotate about a vertical axis figure. No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counter-clockwise and the coil A is as shown at this instant, t = 0, is

A)

constant current clockwise.

B)

varying current clockwise.

C)

varying current counter-clockwise.

D)

constant current counter-clockwise.

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6)

The polarity of induced emf is defined by

A)

Ampere's circuital law.

B)

Biot-Savart law.

C)

Lenz's law.

D)

Fleming's right hand rule.

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7)

Lenz's law is consequence of the law of conservation of

A)

Charge

B)

mass

C)

energy

D)

momentum

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8)

The magnetic flux linked with a coil is given by an equation \[\phi =5{{t}^{2}}+2t+3\]. The induced e.m.f. in the coil at the third second will be

A)

32 units

B)

54 units

C)

40 units

D)

65 units

View Solution

9)

The self-inductance L of a solenoid of length I and area of cross-section A, with a fixed number of turns N increases as

A)

I and A increase.

B)

I decreases and A increases.

C)

I increases and A decreases.

D)

both I and A decrease.

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10)

An iron-cored solenoid has self-inductance 2.8H. When the core is removed, the self-inductance becomes 2 mH. The relative permeability of the material of the core is

A)

1400

B)

1200

C)

2800

D)

2000

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11)

In which of the following application, eddy current has no role to play?

A)

Electric power meters

B)

Induction furnace

C)

LED lights

D)

Magnetic brakes in trains

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12)

Which one of the following statements is wrong?

A)

Eddy currents are produced in a steady magnetic field.

B)

Eddy current is used to produce braking force

C)

Eddy currents is minimized by using l aminated core.

D)

Induction furnace uses eddy current to produce heat

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13)

If the back e.m.f. induced in a coil, when current changes from 1A to zero in one millisecond, is 5 volts, the self-inductance of the coil is

A)

5 H

B)

1 H

C)

5\[\times {{10}^{-3}}\operatorname{H}\]

D)

5\[\times {{10}^{3}}\operatorname{H}\]

View Solution

14)

Magnetic field energy stored in a coil is

A)

\[{{\operatorname{Li}}^{2}}\]

B)

\[\frac{1}{2}\operatorname{Li}\]

C)

\[\operatorname{Li}\]

D)

\[\frac{1}{2}{{\operatorname{Li}}^{2}}\]

View Solution

15)

If two coils of self inductance \[{{\operatorname{L}}_{1}}\] and \[{{\operatorname{L}}_{2}}\] are coupled together, their mutual inductance becomes

A)

\[\operatorname{M}=k\sqrt{{{\operatorname{L}}_{1}}{{L}_{2}}}\]

B)

\[\operatorname{M}=k\sqrt{\frac{{{L}_{1}}}{{{L}_{2}}}}\]

C)

\[\operatorname{M}=k\sqrt{{{\operatorname{L}}_{1}}+{{L}_{2}}}\]

D)

None of the above

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16)

An inductor and a bulb are connected in series with a dc source. A soft iron core is then inserted in the inductor. What will happen to intensity of the bulb?

A)

Intensity of the bulb remains the same.

B)

Intensity of the bulb decreases.

C)

Intensity of the bulb increases

D)

The bulb ceases to glow.

View Solution

12th Class Physics Electro Magnetic Induction Question Bank

done MCQs - Electromagnetic Induction Total Questions - 16

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MCQs - Electromagnetic Induction

MCQs - Electromagnetic Induction Total Questions - 16