Electromagnetic Induction

⚡ What is Electromagnetic Induction?

Electromagnetic induction is the process of producing electricity using magnetism. It was discovered in 1831 by Michael Faraday. This discovery led to the invention of generators, which are used in power stations to produce electricity.

🔬 Key Experiments to Understand Electromagnetic Induction

🧲 1. Straight Wire and U-Shaped Magnet

• A wire is placed between the poles of a U-shaped magnet.

• When the wire is moved up or down, the galvanometer (meter) shows a deflection → a current is induced.

• The current stops when the wire stops moving.

• Direction of current depends on the direction of motion.

✅ Conclusion: Moving a wire through a magnetic field induces a current in the wire.

🧲 2. Bar Magnet and Coil

• A magnet is pushed into a coil → current flows in one direction.

• Magnet is held still inside the coil → no current.

• Magnet is pulled out → current flows in the opposite direction.

• Same effect happens if the coil is moved instead of the magnet.

✅ Conclusion: An e.m.f. (electromotive force) is induced when there is relative motion between the magnet and coil.

📈 What Affects the Size of the Induced e.m.f.?

Faraday found that the size of the induced e.m.f. depends on:

1. Speed of motion (faster = bigger e.m.f.)

2. Number of turns in the coil (more turns = bigger e.m.f.)

3. Strength of the magnet (stronger = bigger e.m.f.)

🧠 Key Idea:

The size of the induced e.m.f. is directly proportional to the rate at which magnetic field lines are cut.

🔄 Direction of the Induced e.m.f. (Lenz’s Law)

• The induced current always opposes the motion that causes it.
  This follows the Law of Conservation of Energy.

Example:

• Moving a north pole into a coil → the coil becomes a north pole to oppose the motion (like poles repel).

• Pulling the magnet out → the coil becomes a south pole to try to pull the magnet back.

✅ This opposing effect prevents energy from being created out of nothing.

👉 Fleming’s Right-Hand Rule (Dynamo Rule)

This rule helps us find the direction of the induced current in a moving wire:

ThuMb → Motion of wire
First finger → Magnetic Field (N to S)
SeCond finger → Induced Current

✋ Remember:
Use your right hand and hold your thumb and fingers at right angles to each other.

🔑 Key Definitions

Electromagnetic induction:

The process of generating an e.m.f. (and possibly a current) in a conductor due to a changing magnetic field or movement across it.

Fleming’s Right-Hand Rule:

A rule used to find the direction of the induced current in a conductor moving at right angles to a magnetic field.

📝 Summary

Action	Result
Move wire through magnetic field	Induces current
Magnet into coil	Current in one direction
Magnet out of coil	Current in opposite direction
No motion	No current
Faster movement	Bigger e.m.f.
More coil turns	Bigger e.m.f.
Stronger magnet	Bigger e.m.f.
Induced current direction	Opposes the cause of the motion (Lenz's Law)