Electro-Magnetic Induction (EMI)

Topics to focus on -Magnetic Flux (Ф)

Faraday’s law of EMI

Induced emf in moving conductor

Self inductance (L) & Mutual inductance (M)

Self inductance of a solenoid

Mutual inductance of a pair of solenoids

Efficiency of a transformer

Magnetic Flux (Ф)

Faraday’s Law of EMI

Induced emf in a moving conductor

Self Inductance (L) & Mutual Inductance (M)

Self Inductance of a Solenoid

Mutual Inductance of a pair of Solenoids

Efficiency of a transformer (η)

A

B

D

C

Q. A metallic rod of length ‘l’ is tied to a string of length 2l and made to rotate with angular speed ധ on a horizontal table with one end of the string fixed. If there is a vertical magnetic field 'B' in the region, the e.m.f induced across the ends of the rod is

JEE 2013

A

B

D

C

Q. The flux linked with a coil at any instant ‘t' is given by Ф = 10t2 - 50t + 250. The induced emf at t= 3s is

JEE 2006

A

B D

C

Q. In a coil of resistance 100Ω, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is

JEE 2017

Q. A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 radians per second. If the horizontal component of earth's magnetic field is 0.2 x 10-4 T, then the e.m.f. developed between the two ends of the conductor is

JEE 2004

A

B

D

C

Q. A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A magnetic induction B constant in time and space, pointing perpendicular and into the plane at the loop exists everywhere with half the loop outside the field, as shown in figure. The induced emf is

JEE 2002

A

B D

C

Q. A power transmission line feeds input power at 2300V to a step down transformer with its primary windings having 4000 turns giving the output power at 230V. If the current in the primary of the transformer is 5A and its efficiency is 90% the output current would be

JEE 2018

A

B

D

C

45A

20A

25A

50A

Q. There are two long coaxial solenoids of same length I. The inner and outer coils have radii r1 and r2 and number of turns per unit length n1 and n2 respectively. The ratio of mutual inductance to the self-inductance of the inner-coil is

JEE 2019

A

B

D

C

Q. A conducting circular loop made of a thin wire, has area 3.5 x 10-3 m2 and resistance 10 Ω. It is placed perpendicular to a time dependent magnetic field B(t) = (0.4 T) sin (50𝜋t). The field is uniform in space. Then, the net charge flowing through the loop during t = 0 s and t = 10 ms is close to

JEE 2019

A

B

D

C

140 μC

21 mC

6 mC

7 mC

Q. One conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure . If each tube moves towards the other at a constant speed v, then the emf induced in the circuit in terms of B, I and v where I is the width of each tube, will be

JEE 2005

A

B

D

C

-Blv

2 Blv

zero

Blv

SMCC