An electron moves on a
straight line path XY as shown in the figure. The coil *abcd* is adjacent
to the path of the electron. What will be the direction of current, if any,
induced in the coil?

**A. ** The current will reverse its direction as the electron goes past the coil

**B. ** No current will be induced

**C. ** abcd

**D. ** adcb

**Answer : ****Option A**

**Explaination / Solution: **

Workspace

Report

A thin semi-circular conducting ring (PQR) of radius r is falling
with its plane vertical in a horizontal magnetic field B, as shown in the
figure.

Workspace

Report

The flux linked with a coil
at any instant t is given by Φ_{B} = 10*t* ^{2} − 50*t* + 250. The induced emf at t = 3s is

**A. ** −190 V

**B. ** −10 V

**C. ** 10 V

**D. ** 190 V

**Answer : ****Option B**

**Explaination / Solution: **

Workspace

Report

When the current changes
from +2A to **−**2A in 0.05 s, an emf of 8 V is induced in a coil. The
co-efficient of self-induction of the coil is

**A. ** 0.2 H

**B. ** 0.4 H

**C. ** 0.8 H

**D. ** 0.1 H

**Answer : ****Option D**

**Explaination / Solution: **

Workspace

Report

The current *i*
flowing in a coil varies with time as shown in the figure. The variation of
induced emf with time would be

**A. **

**B. **

**C. **

**D. **

**Answer : ****Option A**

**Explaination / Solution: **

Workspace

Report

A circular coil with a
cross-sectional area of 4 cm^{2} has 10 turns. It is placed at the
centre of a long solenoid that has 15 turns/cm and a cross-sectional area of 10
cm^{2}. The axis of the coil coincides with the axis of the solenoid.
What is their mutual inductance?

**A. ** 7.54 µH

**B. ** 8.54 µH

**C. ** 9.54 µH

**D. ** 10.54 µH

**Answer : ****Option A**

**Explaination / Solution: **

Workspace

Report

In a transformer, the number of turns in the primary and the secondary are 410 and 1230 respectively. If the current in primary is 6A, then that in the secondary coil is

**A. ** 2 A

**B. ** 18 A

**C. ** 12 A

**D. ** 1 A

**Answer : ****Option A**

**Explaination / Solution: **

Workspace

Report

A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A. Then its efficiency is

**A. ** 1.2

**B. ** 0.83

**C. ** 0.12

**D. ** 0.9

**Answer : ****Option B**

**Explaination / Solution: **

Workspace

Report

In an electrical circuit, *R,
L, C* and AC voltage source are all connected in series. When *L* is
removed from the circuit, the phase difference between the voltage and current
in the circuit is π /3 . Instead, if C is removed from the circuit,
the phase difference is again π / 3 . The power factor of the circuit is

**A. ** 1 / 2

**B. ** 1/ √2

**C. ** 1

**D. ** √3 / 2

**Answer : ****Option C**

**Explaination / Solution: **

Workspace

Report

In a series RL circuit, the resistance and inductive reactance are the same. Then the phase difference between the voltage and current in the circuit is

**A. ** π/4

**B. ** π/2

**C. ** π/6

**D. ** zero

**Answer : ****Option A**

**Explaination / Solution: **

Workspace

Report