Electromagnetic Induction

Previous Years' CBSE Board Questions

6.3 Magnetic Flux

VSA. (1 mark)

1 A long straight current carrying wire passes normally through the centre of circular loop. If the current through the wire increases, will there be an induced emf in the loop? Justify. (Delhi 2017)

(AI 2017)

6.4 Faraday's Law of Induction

MCO

The direction of induced current in the loop abc is:

(Delhi 2015C

1. along abc if I decreases
2. along acb if I increases
3. along abc if I constant
4. along abc if I increases (2023) U А R

1. A square shaped coil of side 10 cm, having 100 turns is placed perpendicular to a magnetic field which is increasing at 1 T/s. The induced emf in the coil is
2. 0.1 V (b) 0.5 V (c) 0.75 V (d) 1.0 V

(2023)

X 26 ×

1. A coil of area 100 cm² is kept at an angle of 30° with a magnetic field of 10^-1 T. The magnetic field is reduced to zero in 10^-4 s. The induced emf in the coil is
2. 5√3 V (b) 50√3 V
3. 5.0 V (d) 50.0 V

X 10 30. 30. 30 36 300

(Term I 2021-22) (Ap)

× 30 36 × 36 30

6.5 Lenz's Law and Conservation of Energy

VSA (1 mark)

Predict the polarity of the capacitor in the situation described below:

What is the direction of induced currents in

metal rings 1 and 2 when current I in the wire is

increasing steadily?

1. Figure shows a current carrying solenoid moving towards a conducting loop. Find the direction of the current induced in the loop.
2. The electric current flowing in a wire in the direction from B to A is decreasing. Find out the direction of the induced current in the metallic loop kept above the wire as shown.

(Al 2014)

10. A flexible wire of irregular shape, abcd, as shown

in the figure, turns into a circular shape when

placed in a region of magnetic field which is

directed normal to the plane of the loop away

from the reader. Predict the direction of the induced

current in the wire.

(Foreign 2014)

SAI (2 marks)

11. Two identical circular discs, one of copper and

another of aluminium, are rotated about their

(AI 2017) (Ap

1. A bar magnet is moved in the direction indicated by the arrow between two coils PQ and CD. Predict the direction of the induced current in each coil.

00000

(2/5, AI 2015C)

(Al 2017)

Describe a simple experiment (or activity) to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it.

(2/5, Delhi 2014) (An OR State Lenz's law. Give one example to illustrate this law. "The Lenz's law is a consequence of the principle of conservation of energy". Justify this statement.

(3/5, Al 2014)

× × × p× ×

x x x x x x x

38 × × × × × × ×

6.6 Motional Electromotive Force

× ××

× × × × × × ×

V5A (1 mark)

34 <math>\times</math> <math>\times</math> <math>\times</math> <math>\times</math>

1. A conducting rod of length I is kept parallel to a uniform magnetic field B. It is moved along the magnetic field with a velocity v . What is the value of

emf induced in the conductor? (2020)

<math>\times M \times</math> × x x xQx x

(Delhi 2014C) (An

A metallic rod PQ of length l is rotated with an angular velocity ω about an axis passing through its mid-point

1. and perpendicular to the plane of the paper, in

uniform magnetic field <math>\vec{B}</math>, as shown in the figure. What is the potential difference developed between the two ends of the rod, P and Q?

× <math>\times</math> <math>\times</math> 0

30 30 130 30 (2020) [1]

Plot a graph showing variation of induced e.m.f. with

geometrical axes with same angular speed in the

same magnetic field acting perpendicular to their

planes. Compare the (i) induced emf, and (ii) induced

current produced in discs between its centre and

edge. Justify your answers. (2021C)

LA (5 marks)

12. State Lenz's law. Use it to predict the polarity of the

capacitor in the situation given below:

20. A rectangular loop PQMN with movable arm PQ

of length 10 cm and resistance 2 <math>\Omega</math> is placed in a

uniform magnetic field of 0.1 T acting perpendicular

to the plane of the loop as is shown in the figure. The

resistances of the arms MN, NP and MQ are negligible.

Calculate the (i) emf induced in the arm PQ and

(ii) current induced in the loop when arm PQ is moved

with velocity 20 m/s.

SAII (3 marks)

1. A rectangular conductor MNPQ with a movable arm MN (resistance r) is kept in a uniform magnetic field as shown in the figure. Resistance of arms MQ, QP an PN are negligible. Obtain the expression for the:
2. current induced in the loop specifying its direction, and
3. power required to move the arm.

<u> </u>

× <math display="block">\begin{array}{c|ccccccccccccccccccccccccccccccccccc</math>

X × × × × × × × ×

(2023)