Electromagnetic Induction Chapter-Wise Test 10

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A rectangular loop of sides 25 cm and 10 cm moves out of a 0.5 T field at 1.5 m/s perpendicular to the longer side. What is the motional emf?

\( \varepsilon = B l v \), \( l = 0.1 \, \text{m} \).

\( \varepsilon = 0.5 \times 0.1 \times 1.5 = 0.075 \, \text{V} \).

0.075 V
0.08 V
0.09 V
0.1 V
1

A coil with \( L = 0.35 \, \text{H} \) has its current increased from 0 to 5 A in 0.5 s. What is the energy stored?

\( W = \frac{1}{2} L I^2 = \frac{1}{2} \times 0.35 \times (5)^2 = 0.175 \times 25 = 4.375 \, \text{J} \approx 4.38 \, \text{J} \).

4 J
4.2 J
4.3 J
4.38 J
4

A coil with a high self-inductance is connected to a battery. Why does the current take time to reach its maximum value?

High self-inductance induces a back emf that opposes the increase in current, slowing the rate at which the current builds up to its steady-state value.

Due to resistance of the coil
Due to low battery voltage
Due to back emf opposing current change
Due to thermal effects
3

A solenoid with mutual inductance 0.15 H has a current change of 8 A/s in the primary coil. What is the induced emf in the secondary coil?

\( \varepsilon = M \frac{dI}{dt} = 0.15 \times 8 = 1.2 \, \text{V} \).

0.8 V
1.0 V
1.2 V
1.4 V
3

A square loop of side 24 cm rotates at 15 rad/s in a 0.25 T field. What is the maximum emf induced?

\( A = (0.24)^2 = 0.0576 \, \text{m}^2 \).

\( \varepsilon_0 = N B A \omega = 1 \times 0.25 \times 0.0576 \times 15 = 0.216 \, \text{V} \).

0.18 V
0.216 V
0.25 V
0.3 V
2

A metal plate swings like a pendulum through a magnetic field. The slowing of its motion is primarily due to what?

The motion induces currents in the plate, which produce an opposing magnetic field, exerting a force that resists the motion (Lenz’s law), slowing it down.

Gravitational force
Frictional resistance
Electrostatic repulsion
Opposing force from induced currents
4

A rod rotates at 22 rad/s in a 0.4 T field. If the length from the axis to the tip is 0.6 m, what is the emf induced?

\( \varepsilon = \frac{1}{2} B \omega R^2 \).

\( \varepsilon = \frac{1}{2} \times 0.4 \times 22 \times (0.6)^2 = 1.584 \, \text{V} \approx 1.58 \, \text{V} \).

1.2 V
1.4 V
1.58 V
1.6 V
3

A coil is connected to a DC source via a switch. When the switch is opened, a spark is observed. This is due to what phenomenon?

Opening the switch causes a rapid decrease in current, inducing a high back emf due to self-inductance, which can cause a spark as the energy dissipates.

Electrostatic discharge
Magnetic saturation
Thermal expansion
High back emf from self-inductance
4

A coil of 120 turns experiences a magnetic flux change from 0 to 0.04 Wb in 0.08 s. What is the induced emf?

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

\( \Delta \Phi = 0.04 \, \text{Wb} \), \( \Delta t = 0.08 \, \text{s} \), \( N = 120 \).

\( \varepsilon = 120 \times \frac{0.04}{0.08} = 120 \times 0.5 = 60 \, \text{V} \).

60 V
65 V
70 V
75 V
1

A rectangular loop of 0.26 m × 0.42 m moves out of a 0.45 T field at 0.7 m/s along its shorter side. What is the emf?

\( \varepsilon = B l v \), \( l = 0.42 \, \text{m} \).

\( \varepsilon = 0.45 \times 0.42 \times 0.7 = 0.1323 \, \text{V} \approx 0.132 \, \text{V} \).

0.1 V
0.12 V
0.13 V
0.132 V
4

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