Electromagnetic Induction Chapter-Wise Test 11

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A coil of 180 turns and area 0.09 m² is in a field that decreases from 0.11 T to 0 in 0.6 s. What is the induced emf?

\( \Delta \Phi = B A = 0.11 \times 0.09 = 0.0099 \, \text{Wb} \).

\( \varepsilon = N \frac{\Delta \Phi}{\Delta t} = 180 \times \frac{0.0099}{0.6} = 180 \times 0.0165 = 2.97 \, \text{V} \).

2.5 V
2.97 V
3.2 V
3.5 V
2

A rod rotates at 16 rad/s in a 0.6 T field. If the length from the axis to the tip is 0.5 m, what is the emf induced?

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

\( \varepsilon = \frac{1}{2} \times 0.6 \times 16 \times (0.5)^2 = 1.2 \, \text{V} \).

0.8 V
1.0 V
1.2 V
1.4 V
3

A magnet is oscillated near a coil. The induced emf in the coil alternates because of what characteristic of the magnet’s motion?

The oscillatory motion causes the magnetic flux to alternately increase and decrease, inducing an alternating emf as the flux change direction reverses.

Constant speed
Periodic change in flux direction
Steady magnetic field
Random motion
2

A rectangular loop of sides 28 cm and 14 cm moves out of a 0.7 T field at 1.2 m/s perpendicular to the longer side. What is the motional emf?

\( \varepsilon = B l v \), \( l = 0.14 \, \text{m} \).

\( \varepsilon = 0.7 \times 0.14 \times 1.2 = 0.1176 \, \text{V} \approx 0.118 \, \text{V} \).

0.118 V
0.13 V
0.15 V
0.17 V
1

A rod rotates at 18 rad/s in a 0.4 T field. If the length from the axis to the tip is 0.7 m, what is the emf induced?

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

\( \varepsilon = \frac{1}{2} \times 0.4 \times 18 \times (0.7)^2 = 1.764 \, \text{V} \approx 1.76 \, \text{V} \).

1.5 V
1.6 V
1.76 V
1.8 V
3

A coil of 250 turns rotates at 80 rad/s in a 0.04 T field. If the area is 0.015 m², what is the maximum emf?

\( \varepsilon_0 = N B A \omega = 250 \times 0.04 \times 0.015 \times 80 = 12 \, \text{V} \).

8 V
10 V
11 V
12 V
4

A loop of 0.4 m × 0.18 m moves out of a 0.5 T field at 1.8 m/s along its longer side. How long does the emf last?

Time = distance/velocity, distance = width along motion = 0.18 m.

\( t = \frac{0.18}{1.8} = 0.1 \, \text{s} \).

0.08 s
0.09 s
0.1 s
0.12 s
3

A coil of 140 turns and area 0.02 m² is rotated at 25 Hz in a 0.07 T field. What is the maximum emf?

\( \omega = 2\pi v = 2\pi \times 25 = 50\pi \, \text{rad/s} \).

\( \varepsilon_0 = N B A \omega = 140 \times 0.07 \times 0.02 \times 50\pi = 30.79 \, \text{V} \approx 30.8 \, \text{V} \).

28 V
29 V
30 V
30.8 V
4

A solenoid of 500 turns per meter and area 0.02 m² has a current drop from 6 A to 3 A in 0.25 s. What is the self-induced emf? (\( \mu_0 = 4\pi \times 10^{-7} \, \text{H/m} \))

\( L = \mu_0 n^2 A l \), assume \( l = 1 \, \text{m} \).

\( L = 4\pi \times 10^{-7} \times (500)^2 \times 0.02 \times 1 = 0.00628 \, \text{H} \).

\( \varepsilon = L \frac{\Delta I}{\Delta t} = 0.00628 \times \frac{3 - 6}{0.25} = 0.00628 \times (-12) = 0.07536 \, \text{V} \approx 0.075 \, \text{V} \).

0.06 V
0.075 V
0.09 V
0.1 V
2

A flat coil is placed in a magnetic field that decreases with time. The direction of the induced current is such that it produces a magnetic field in which direction?

Lenz’s law dictates that the induced current opposes the decrease in flux by producing a magnetic field in the same direction as the original field.

Perpendicular to the original field
Opposite to the original field
Random direction
Same as the original field
4

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