Class 12 > Unit # 19:Electromagnetic Induction > Electromagnetic Induction & Induced EMF

Electromagnetic Induction & Induced EMF — Unit 19

Welcome to Talha's Physics Academy. In this lecture, we explore how electricity is generated using magnetism through the fundamental process of electromagnetic induction.

Video Lecture

1. What is Electromagnetic Induction?

Electromagnetic induction is the process by which a voltage or electromotive force (EMF) is produced in an electrical conductor when the magnetic field surrounding it changes, or when the conductor moves relative to a magnetic field.

• Requirements: A magnetic field and a conductor.
• Mechanism: Either the magnetic field is kept stationary while the conductor moves, or the conductor is stationary while the magnetic field changes.

2. Michael Faraday's Experiment

Michael Faraday discovered that relative motion between a magnet and a coil of wire induces a current:

• Moving a magnet towards a coil induces an EMF, causing a galvanometer to deflect in one direction.
• Moving the magnet away from the coil induces an EMF in the opposite direction.
• When the magnet is stationary relative to the coil, the induced current drops to zero.

3. Two Primary Ways to Induce EMF

A. The Generator Effect (Motional EMF)

The EMF is induced due to the relative mechanical motion between a conductor and a magnetic field. As the conductor moves through the magnetic field lines, the magnetic flux linked with the coil changes, generating electricity (as seen in AC/DC generators).

B. The Transformer Effect

Neither the magnet nor the conductor moves physically. Instead, the strength or orientation of the magnetic field surrounding a stationary conductor is varied (commonly using an alternating current in a primary coil to induce an EMF in a secondary coil).

$$\text{Induced EMF} \propto \frac{\Delta \Phi}{\Delta t}$$

This foundational principle powers everything from large-scale power plant generators to everyday transformers and electronic devices.