Electromagnetic Induction Chapter-Wise Test 3

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A coil of 110 turns experiences a magnetic flux change from 0 to 0.05 Wb in 0.1 s. What is the induced emf?

\( \varepsilon = N \frac{\Delta \Phi}{\Delta t} \).

\( \Delta \Phi = 0.05 \, \text{Wb} \), \( \Delta t = 0.1 \, \text{s} \), \( N = 110 \).

\( \varepsilon = 110 \times \frac{0.05}{0.1} = 110 \times 0.5 = 55 \, \text{V} \).

55 V
60 V
65 V
70 V
1

A conducting loop is moved into a uniform magnetic field region. During the entry, the induced current flows in a direction determined by what?

The direction opposes the increase in flux as the loop enters, governed by Lenz’s law, which ensures the current resists the change.

Faraday’s law
Lenz’s law
Ampere’s law
Gauss’s law
2

A coil connected to a DC source shows a slow rise in current when switched on. This delay is primarily due to what effect?

Self-inductance induces a back emf that opposes the current increase, causing a gradual rise until the steady state is reached.

Resistance of the coil
Back emf from self-inductance
Capacitance in the circuit
Magnetic saturation
2

A rod of length 0.7 m moves at 2 m/s in a 0.3 T field perpendicular to its length. What is the induced emf?

\( \varepsilon = B l v = 0.3 \times 0.7 \times 2 = 0.42 \, \text{V} \).

0.42 V
0.45 V
0.5 V
0.55 V
1

A coil with \( L = 0.45 \, \text{H} \) has its current increased from 0 to 8 A in 0.8 s. What is the energy stored?

\( W = \frac{1}{2} L I^2 = \frac{1}{2} \times 0.45 \times (8)^2 = 0.225 \times 64 = 14.4 \, \text{J} \).

13 V
13.5 V
14 V
14.4 V
4

A loop of 0.25 m × 0.15 m moves out of a 0.2 T field at 1.5 m/s along its longer side. How long does the emf last?

Time = distance/velocity, distance = width along motion = 0.15 m.

\( t = \frac{0.15}{1.5} = 0.1 \, \text{s} \).

0.05 s
0.08 s
0.1 s
0.12 s
3

Two coils are placed close to each other. When the current in one coil is changed, an emf is induced in the other. This phenomenon is known as what?

This is mutual induction, where a changing current in one coil induces an emf in a nearby coil due to the changing magnetic flux linking them.

Mutual induction
Self-induction
Electrostatic induction
Magnetic resonance
1

A rectangular loop of 0.2 m × 0.35 m moves out of a 0.4 T field at 0.8 m/s along its shorter side. What is the emf?

\( \varepsilon = B l v \), \( l = 0.35 \, \text{m} \).

\( \varepsilon = 0.4 \times 0.35 \times 0.8 = 0.112 \, \text{V} \).

0.09 V
0.1 V
0.11 V
0.112 V
4

A circular loop of radius 18 cm is deformed into a straight wire in a 0.14 T field in 0.7 s. What is the induced emf?

Initial flux: \( \Phi = B A = 0.14 \times \pi \times (0.18)^2 = 0.01425 \, \text{Wb} \).

Final flux = 0.

\( \varepsilon = \frac{\Delta \Phi}{\Delta t} = \frac{0.01425}{0.7} = 0.02036 \, \text{V} \approx 0.02 \, \text{V} \).

0.015 V
0.02 V
0.025 V
0.03 V
2

A coil of 160 turns and area 0.025 m² is rotated at 20 Hz in a 0.09 T field. What is the maximum emf?

\( \omega = 2\pi v = 2\pi \times 20 = 40\pi \, \text{rad/s} \).

\( \varepsilon_0 = N B A \omega = 160 \times 0.09 \times 0.025 \times 40\pi = 45.24 \, \text{V} \).

42 V
43 V
44 V
45.24 V
4

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