Boost up your IIT JEE preparation by exploring the world of electromagnetic induction with the help of various tips offered by askIITians experts. Click here to know more:

1. Electromagnetic Induction

2. Electromagnetic Induction was first discovered way back in the 1830’s by
Michael Faraday. Faraday noticed that when he moved a permanent magnet
in and out of a coil or a single loop of wire it induced an Electromotive Force
or EMF. In other words a voltage, and therefore a current were produced. So
what Michael Faraday discovered was a way of producing an electrical
current in a circuit by using only the force of a magnetic field and not
batteries. This then lead to a very important law linking electricity with
magnetism, Faraday’s Law of Electromagnetic Induction.

3. The various topics that form a part of electromagnetic
induction include:
 Faraday’s Laws of Electromagnetic Induction
 Lenz’s Law
 Motion of a loop in a uniform magnetic field
 Self-induction and co-efficient of self-induction
 Mutual-induction
 Co-efficient of mutual-induction
 Energy stored in an inductor
 Fleming’s right and left hand rule
 Eddy current
 Alternating current
 Coil rotating in a uniform magnetic field
We shall give a brief outline of these topics in addition to the tips to master them. Those
willing to go into the intricacies can refer the study material page on electromagnetic
induction.

4. Important Formulas

5. Is this a valuable topic for those who are preparing for IIT-JEE,
AIPMT and CBSE Exam?
Electromagnetic induction is one of the easiest topics in physics, and one can
easily score good marks in it. It is foolish to leave the questions from this
section. Moderate levels of questions are coming from this section. The
electromagnetic induction part contributes almost 5% in the IIT-JEE and the
other two exams.
What are the best books for the preparation of
electromagnetic induction?
Some of the books which are considered to be best for preparation of this
section are:
 Resnick Halliday
 I.E. Irodov
 H.C Verma
Problems of varied complexities can be found in the book Resnick Halliday. It
has also a special edition dedicated to IIT-JEE. The standard of Irodov physics
is quite high. At the end, H.C. Verma is quite useful for these examinations.

6. Illustrations
Question 1:- [IIT JEE 2014]
Two ideal batteries of emf V1 and V2 and three resistances R1, R2 and R3 are
connected as shown in the figure. The current in resistance R2 would be zero
if
A.V1 = V2 and R1 = R2 = R3 B.V1 = V2 and R1 = 2R2 = R3
C.V1 = 2V2 and 2R1 = 2R2 = R3 D.2V1 = V2 and 2R1 = R2 = R3
Solution:-
Current through R2 will be zero of Eeqv of two batteries is zero
So, (V1/R1 – V2/R3)/(1/R1 + 1/R3) = 0
Or,V1/R1 = V2/R3
In option (A), V1 = V2 that gives, R1 = R3 whatever be the value
of R2 to maintain image of loop V1 with respect to V2.
Hence, option A and B both are correct. In options, C and D,
using loop analysis method we find,V1/V2 = 2, that satisfied, R3/R1 = 2
This relation is satisfied by option A & B. Hence, A, B and C are correct.

7. Question 2:- [JEE Advanced 2013]
A point Q is moving in a circular orbit of radius R in the x-y plane
with angular velocity ω. This can be considered as equivalent to a
loop carrying a steady current Qω/2π. A uniform magnetic field
along the positive z-axis is now switched on, which increases at a
constant rate from 0 to B in one second. Assume that the radius of
the orbit remains constant. The application of the magnetic field
induces an emf in the orbit. The magnitude of the induced electric
field in the orbit at any instant of time during the time interval of
the magnetic field change, is
A.BR/4 B.BR/2 C.BR D.2BR
Solution:-
E (2πR) = πR2 (dB/dt)
So, E = RB/2
So the option (B) is correct.

8. Some Interesting Facts
 Electromagnetic induction is the production of an electromotive (emf) in
a conductor as a result of a changing magnetic field about the conductor.
 The induced emf is always such that it opposes the change that gives rise
to it, according to Lenz's law.
 Changing the current in a given circuit can also induce an emf in another,
nearby circuit unconnected with the original circuit; this type of
electromagnetic induction, called mutual induction, is the basis of the
transformer.
 Electrostatic induction is the production of an unbalanced electric charge
on an uncharged metallic body.
 Magnetic induction is the production of a magnetic field in a piece of
unmagnetized iron or other ferromagnetic substance when a magnet is
brought near it.

9. Tips to Study Electromagnetic Induction
Electromagnetic induction is one of the important chapter for the IIT-JEE aspirant’s. Often
students doing mistake due to the lack of concept regarding the direction of electric-magnetic
field and induced emf. Below are the some useful tips to handle this topic so
quickly and accurately.
 Always three parameters are involved in an electromagnetic induction problem. One is
magnetic field, second one is a inductor or coil and the third one is movement of coil with
respect to field.
 Basically, in a given problem, two quantities are known and the third quantity needs to be
calculated.
 Before attempting the problem, check the units of all the parameters must belong to any
one standard unit system. That is either in S.I or C.G.S.
 Must aware of the Generator Rule which is the principle to determine the direction of
induced emf of a conductor moving in a magnetic field.
 Know the proper law and some concept regarding the direction of electric and magnetic
field.
 Clear your concept by doing the more and more problem on application of Faraday’s law,
Lenz’s law, Fleming’s right hand and left hand thumb rule for current.

10. Practical Applications of Electromagnetic Induction
 Some electric generators can be driven by human power such as a hand crank or a motor car to
generate electricity by the principle of electromagnetic induction.
 A transformer uses two important connections between electricity and magnetism to convey
power from one AC circuit to another results the application of electromagnetic induction.
 An electric generator which a device for transforming mechanical energy to electrical energy to
generate electricity is one of the applications of electromagnetic induction.
 The bulb in the halogen desk lamp operates from low voltages provided with the help of a
transformer, which based on the theory of electromagnetic induction.
 A hybrid automobile couples together a combustion engine and one or more motor/generators
so that it can convert energy easily between mechanical and electric forms and can operate on
fuel, battery, or both by the help of electromagnetic induction principle.
 Loudspeakers use electromagnets to vibrate the cone and produce sound based on the principle
electromagnetic induction.

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