# Chapter 11 – Electromagnetic Induction

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

Do you know when electromagnetic induction was first discovered? It was first discovered in 1830 by Michael Faraday. He understood the concept of electromagnetic induction by a simple experiment of moving a magnet in and out of the coil. This current was produced, and then he named this phenomenon as Electromagnetic Induction and gave the principle of electromagnetic induction and electromagnetic rotation.

The law states that “a voltage is induced in a circuit whenever relative motion exists between a conductor and a magnetic field and that the magnitude of this voltage is proportional to the rate of change of the flux.”

In simple words, electromagnetic induction generates an electric current in a closed circuit by using magnetic fields.

#### Lenz's Law and Conservation of Energy

The law states, “the direction of an induced EMF is such that it will always oppose the change that is causing it.”

In simple words, the induced current always opposes the motion that started the induced current.

This law also explains the concept of self-induced EMF or back EMF.

Let us see Lenz Law; when you take the magnet’s north pole towards the coil, the coil’s side’s current flow is nearest to the pole and generates opposition to the bar magnet. When you withdraw the magnet from the coil, the current is reversed, and the coil becomes a south pole and attracts the magnet.

Lenz Law follows the conservation of energy. Going by the above explanation, when the magnet is pushed and pulled by the coil because of induced current, a small amount of work is done. Hence, there is a small amount of energy in the form of the heating effect. Thus, it doesn’t violate the conservation of energy.

#### Motional Electromotive Force

To understand Motional EMF, we will take the help of a diagram.

Consider a straight conductor AB that moves through a rectangular coil CDEF. The movement is uniform and time-independent.

Let’s consider that the movement of the rod CB is uniform across the loop CDEF and has a constant velocity in m/s.

Therefore, the rectangle CDEP forms a closed circuit due to the uniform motion of AB.

The magnetic flux ΦB enclosed by the rectangular loop CDEF is written as:

ΦB = Blx

EF = x and CD = l

As the conductor is moving and x is changing with time, the rate of flux ΦB induces voltage or EMF by this formula.

ϵ = −dϕBdt=−ddt(Blx)=−Bldxdt=Blv

Motional Electromotive Force can be induced in 2 ways –

1.   The motion of the conductor in a magnetic field
2.   Change in magnetic flux in an enclosed circuit.

#### Energy Consideration a Quantitative Study

After deriving the above equation, let us see how Lenz Law follows the conservation of energy. We know,

As the loop CDEF is in a magnetic field, there is current in the coil; a force acts on arm CF,

Hence

If the rod AB is pushed with a constant velocity of magnitude v, then the power will be,

Eddy Currents

The induced voltage within the metallic part of the loop, causing the induced current to flow around it, is called Eddy Currents.

Eddy currents are produced by electromagnetic induction as the current circulates the coil’s core or any connecting metallic elements together in the magnetic field.

The induced current flow works like a negative force, producing resistive heating and power loss within the core. It is applied in a furnace, and it is used to heat and melt ferromagnetic metals.

AC Generator

An AC Generator works on the principle of Fleming’s right-hand rule. When the armature rotates between the magnet’s two poles perpendicularly to the magnetic field, the magnetic flux changes in the armature constantly.

Due to this, an EMF or voltage is induced in the armature. It produces a current that flows through the galvanometer, slip rings, and the brushes. The galvanometer will fluctuate between negative and positive numbers. It is proof that the current is alternating.

#### The Experiments of Faraday and Henry

Faraday and Henry conducted three types of experiments.

1. In the first one, Faraday moved a magnet towards a circular coil attached to a galvanometer such that the north pole of the magnet is towards the coil. The result shows that only relative motion generates current in the coil and not when both are kept stationary.
2. In the 2nd experiment, Faraday moved a current-carrying coil towards the first coil, connected to the battery. It was seen that the magnitude of deflection in the galvanometer of the second coil depends on the speed of the coil when it moves.
3. In the 3rd experiment, Faraday had two coils put together, which were stationary. He connected one of them to a galvanometer and the other to a battery. When the current was flowing and switched on the key, the galvanometer showed a deflection, but it didn’t show any deflection when the key was switched off.

#### Conclusion

Electromagnetic Induction is a vital concept of physics and has a host of applications in our day to day life. From induction motors to AC generators, electromagnetic induction applies in a host of operations without which it will not be possible to lead our day to day life.

#### FAQs

What do you mean by electromagnetic induction?

Electromagnetic induction is a current produced due to EMF or voltage production in a constantly changing magnetic field.

What is electromagnetic induction, and how does it work?

Electromagnetic induction is a current produced due to EMF or voltage production in a constantly changing magnetic field. When a magnet is moved through a current containing a coil, it generates an induced voltage.

What is the use of electromagnetic induction?

It is used for a variety of purposes like AC generators, electrical transformers, etc.

What is the basic principle of electromagnetic induction?

The basic principle of Electromagnetic induction is Faraday’s law that states “that a voltage is induced in a circuit whenever relative motion exists between a conductor and a magnetic field and that the magnitude of this voltage is proportional to the rate of change of the flux.”

What are the two laws of electromagnetic induction?

The first law states that “A voltage is induced in a circuit whenever relative motion exists between a conductor and a magnetic field and that the magnitude of this voltage is proportional to the rate of change of the flux.”

The second law states, “the magnitude of EMF or voltage induced in the coil is equal to the rate of change of flux that linkages with the coil. The coil’s flux linkage is the product of the number of turns in the coil and flux associated with the coil.

Wanna learn a little more about this? Would you also like examples? You can check out our MSVgo app to better understand electromagnetic induction concepts with videos and interactive methods!

### High School Physics

• Alternating Current
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### High School Math

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### Middle School Science

• Acids, Bases And Salts
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### Middle School Math

• Area and Its Boundary
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