Electromagnetic Induction Chapter-Wise Test 5

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A flat coil rotates in a uniform magnetic field. The induced emf is zero when the plane of the coil is in which position?

The emf is zero when the rate of flux change is zero (\( \frac{d\Phi}{dt} = 0 \)), which occurs when the coil is parallel to the field (\( \sin\theta = 0 \)).

Perpendicular to the field
At 45° to the field
Parallel to the field
At 30° to the field
3

A rectangular loop of sides 20 cm and 8 cm moves out of a 0.45 T field at 1.2 m/s perpendicular to the shorter side. What is the motional emf?

\( \varepsilon = B l v \), \( l = 0.2 \, \text{m} \).

\( \varepsilon = 0.45 \times 0.2 \times 1.2 = 0.108 \, \text{V} \).

0.108 V
0.12 V
0.14 V
0.16 V
1

A coil with a ferromagnetic core has higher self-inductance compared to an air-core coil. This is primarily due to what property of the core?

The ferromagnetic core increases the magnetic permeability (\( \mu \)), enhancing the magnetic flux linkage and thus increasing self-inductance (\( L = \mu n^2 A l \)).

High electrical conductivity
Low resistance
High density
High magnetic permeability
4

A loop of 0.5 m × 0.22 m moves out of a 0.7 T field at 1.4 m/s along its longer side. How long does the emf last?

Time = distance/velocity, distance = width along motion = 0.22 m.

\( t = \frac{0.22}{1.4} = 0.1571 \, \text{s} \approx 0.16 \, \text{s} \).

0.12 s
0.14 s
0.16 s
0.18 s
3

A circular loop of radius 9 cm is deformed into a straight wire in a 0.25 T field in 0.4 s. What is the induced emf?

Initial flux: \( \Phi = B A = 0.25 \times \pi \times (0.09)^2 = 0.00636 \, \text{Wb} \).

Final flux = 0.

\( \varepsilon = \frac{\Delta \Phi}{\Delta t} = \frac{0.00636}{0.4} = 0.0159 \, \text{V} \approx 0.016 \, \text{V} \).

0.01 V
0.016 V
0.02 V
0.025 V
2

Two coils are arranged such that their mutual inductance is maximized. What is the most likely orientation of their axes?

Mutual inductance is maximized when the magnetic flux from one coil fully links with the other, which occurs when their axes are aligned (coaxial).

Perpendicular to each other
Coaxial
At 45° to each other
Randomly oriented
2

A circular coil of radius 12 cm and 250 turns rotates at 55 rad/s in a 0.025 T field. What is the maximum emf induced?

\( A = \pi r^2 = 3.14 \times (0.12)^2 = 0.0452 \, \text{m}^2 \).

\( \varepsilon_0 = N B A \omega = 250 \times 0.025 \times 0.0452 \times 55 = 15.535 \, \text{V} \approx 15.54 \, \text{V} \).

15.54 V
16.0 V
16.5 V
17.0 V
1

A rod of length 0.3 m moves at 4 m/s in a 0.25 T field perpendicular to its length. What is the induced emf?

\( \varepsilon = B l v = 0.25 \times 0.3 \times 4 = 0.3 \, \text{V} \).

0.3 V
0.4 V
0.5 V
0.6 V
1

A metal disc rotates in a uniform magnetic field perpendicular to its plane. The induced emf between the center and the rim is due to what?

The rotation causes charges in the disc to move through the magnetic field, experiencing a Lorentz force that separates them radially, inducing an emf from center to rim.

Change in magnetic field strength
Electrostatic induction
Thermal motion of charges
Lorentz force on moving charges
4

A coil of 200 turns rotates at 90 rad/s in a 0.04 T field. If the area is 0.015 m², what is the maximum emf?

\( \varepsilon_0 = N B A \omega = 200 \times 0.04 \times 0.015 \times 90 = 10.8 \, \text{V} \).

9 V
10 V
10.5 V
10.8 V
4

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