Electromagnetic Induction

• Electromagnetic induction — induced EMF when magnetic flux through coil changes (Faraday).
• Lenz's law — induced current opposes the change causing it.
• Fleming's right-hand rule — generator rule (motion → current).
• AC generator — basic principle: rotating coil in magnetic field.
• DC vs AC — direction of induced current.

1. Faraday's discovery — relative motion between magnet and coil induces current.
2. Induced EMF — depends on rate of change of magnetic flux (qualitative).
3. Lenz's law — polarity opposes motion of magnet (conservation of energy).
4. Fleming's right-hand rule — thumb = motion, first finger = field, second finger = induced current.
5. AC generator — slip rings; current reverses each half rotation.
6. DC generator — split-ring commutator gives unidirectional current.
7. Galvanometer deflection — detects induced current in NCERT activities.
8. Factors — faster motion, more turns → larger induced EMF.
9. Transformer (intro) — uses mutual induction; step-up/step-down.
10. Real world — power generation, bicycle dynamo, induction stove (intro).

Magnet pushed toward coil — predict induced current direction (Lenz's law)

Step 1 — N pole approaching coil face → flux through coil increases.
Step 2 — Lenz: induced current creates N pole on near face to **repel** approaching magnet.
Step 3 — Use right-hand grip on coil to find current direction.
Step 4 — When magnet withdrawn, current reverses (flux decreasing).
Step 5 — No relative motion → no induced EMF.
Conclusion: induced current always opposes change in flux.

• Thinking steady magnet near coil induces current (need changing flux).
• Using left-hand rule for generator (need right-hand).
• Misconception: Lenz law violates energy conservation (it enforces it).
• Confusing self and mutual induction.
• Believing faster motion doesn't affect induced EMF magnitude.

• State Faraday's observation in words.
• What does Lenz's law tell us?
• Difference between AC and DC generator output.
• When is EMF induced in a coil?

Open the Practice tab for graded questions on Electromagnetic Induction.