Top 10 Questions

## Electromagnetic Induction

- Running short of time? Practice top 10 questions of the chapter and boost your confidence.
1
Calculate the induced emf in a closed loop.

In Figure , a stiff wire bent into a semicircle of radius a = 2.0 cm is rotated at constant angular speed 40 rev/s in a uniform 20 mTmagnetic field. What are the (a) frequency and (b) amplitude of the emf induced in the loop?

2
Problems on gauss law and faraday law Lenz's law.
A train is moving from south to north with a velocity of km/h. The vertical component of earth's magnetic induction is If the distance between the two rails is what is the induced e.m.f. in its axle?
A
B
C
D
3
Solve problem on moving conductor with a constant velocity in a circuit with capacitor.
A pair of parallel horizontal conducting rails ot negligible resistance connected to a capacitor is fixed on a table.The distance between the rails is A conducting rod of mass can slide on the rails frictionlessly. The rod is tied at midpoint to a light string passing over a smooth pulley fixed to the edge of the table. A mass of tied to the other end of the string hangs vertically as shown in the Figure. A uniform magnetic field of can be applied in vertically downward direction. If the system is released from rest, then, point out incorrect statements from the following:

[ being the acceleration due to gravity]
This question has multiple correct options
A
When the magnetic field is put on, the acceleration of the system increases from to
B
Due to induction, the change in the acceleration of the system is same as that obtained by increasing the mass of the rod by in the absence of the magnetic field.
C
Due to induction, the change in the acceleration of the system is same as that obtained by decreasing the mass of the rod by in the absence of magnetic field.
D
When the magnetic field is put on, the acceleration of the system decreases from to
4
Problem on Mutual Inductance

An e.m.f. of 15 V is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of currents at time and second is

A
B
C
D
5
The magnetic induction at the point . If the wire carries a current , is
A
B
C
D
6
Calculate mutual inductance of two inductors of different shapes.
A circular loop of radius lies parallel to a much bigger circular loop of radius . The centre of the small loop is on the axis of the bigger loop. The distance between their centres is . If a current of flows through the smaller loop, then the flux linked with bigger loop is
A
B
C
D

7
Calculate the effective inductance of inductors in series and parallel.
This circuit is equivalent to a single inductor having inductance . Determine the value of the inductance .
A
B
C
D
8
Given
Neglecting mutual inductance, the time constants (in ms) for circuits (i), (ii), and (iii) are:
A
B
C
1, 1, 1
D
9
Solve problems on LR circuits involving multiple resistors and inductors.
The current through the inductor after a long time will be
A
zero
B
infinite
C
D
none of these
10
Calculate the emf induced in an AC generator.
An ac generator has emf  , with    and  . It is connected to a    inductor. (a) What is the maximum value of the current? (b) When the current is a maximum, what is the emf of the generator? (c) When the emf of the generator is  and increasing in magnitude, what is the current?