In this lecture, we focus on mutual induction and explore major applications of electromagnetic induction including the AC generator, AC motor, eddy currents, and back EMF.

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🔁 Mutual Induction

Mutual induction occurs when a changing current in one coil induces an EMF in another nearby coil.

A change in current in the primary coil produces a changing magnetic field, which induces EMF in the secondary coil.

Mathematically:

ε=−MdIdt\varepsilon = -M \frac{dI}{dt}ε=−MdtdI​

where:

• $M$ = mutual inductance

• dIdt\frac{dI}{dt}dtdI​ = rate of change of current

📌 Applications:

• Transformers

• Induction coils

• Wireless charging systems

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⚙️ AC Generator

An AC generator converts mechanical energy into electrical energy using electromagnetic induction.

🔹 Working Principle:

Based on Faraday’s Law of Electromagnetic Induction.

When a coil rotates in a magnetic field:

• Magnetic flux changes continuously

• Alternating EMF is produced

Induced EMF:

$$\epsilon =NAB\omega \sin \omega t$$

where:

• $N$ = number of turns

• $A$ = area of coil

• $B$ = magnetic field

• $\omega$ = angular velocity

It produces alternating current (AC).

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🔄 AC Motor

An AC motor converts electrical energy into mechanical energy.

🔹 Working Principle:

Based on the force experienced by a current-carrying conductor in a magnetic field.

• Alternating current produces rotating magnetic field

• This causes continuous rotation of the coil

Used in:

• Fans

• Washing machines

• Industrial machines

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🔋 Back EMF

When a motor rotates:

• The rotating coil cuts magnetic flux

• An induced EMF is produced in opposite direction

• This is called Back EMF

Back EMF:

• Opposes applied voltage

• Regulates current automatically

• Prevents excessive current flow

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🔥 Eddy Currents

Eddy currents are circular currents induced in a conductor when magnetic flux changes.

🔹 Applications:

• Electromagnetic braking

• Induction heating

• Energy meters

To reduce energy loss due to eddy currents, laminated cores are used.

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🎯 By the End of This Lecture

You will:

• Understand mutual induction and its applications

• Explain working of AC generator

• Describe operation of AC motor

• Understand concept of back EMF

• Explain eddy currents and their uses

This lecture connects electromagnetic induction with practical electrical machines used in daily life and industry.