Motion Makes Current

Why it matters

Faraday shoved a magnet into a coil and a meter twitched. He held it still — dead. Out — twitch, the other way. The universe pays for current with CHANGE, never with mere presence.

The idea in plain words

The generator's birth certificate. Tap the terms.

e.m.f. ∝ rate of change of flux

Why does pushing a magnet into a coil feel slightly 'springy'?

The resistance you feel is the electricity being paid for

• the size: Faraday's law — faster change (speed, stronger magnet, more turns) → bigger induced e.m.f.
• the direction: Lenz's law — induced current opposes the change causing it — push in, it pushes back
• the tool: Fleming's RIGHT hand — thuMb motion, First finger field → seCond finger gives induced current
• the machine: a.c. generator — spin a coil in a field: the flux change reverses each half turn → alternating current
• Lenz: the induced current makes the coil's face repel the incoming pole
• You do work against it — THAT work becomes the electrical energy

Predict first

A strong magnet rests INSIDE a coil, motionless. The induced current is…

Induction needs CHANGING magnetic flux. The strongest magnet sitting still induces exactly nothing — the meter only moves when the magnet does.

• zero — no change in flux, no current — correct
• large and steady — strong magnet, strong current
• small but steady

What you do

Move the magnet fast, slow, in, out — then hold it still inside the coil and watch the meter die.

Check yourself

To induce a LARGER e.m.f., do any of these except…

Speed, turns, stronger magnet all raise the RATE of change. Stillness sets it to zero.

a.c. differs from d.c. in that a.c. …

The mains alternates at 50 Hz because the generator coil flips its flux 50 times a second.

The current induced by pushing a magnet's N pole toward a coil face makes that face…

Lenz's law is nature refusing free energy: the coil resists the very change that feeds it.

• hold the magnet perfectly still inside the coil — correct
• move the magnet faster
• use a coil with more turns
• reverses direction periodically (50 times a second in India) — correct
• is always at higher voltage
• flows only in thin wires
• a N pole — to oppose (repel) the approach — correct
• a S pole — to welcome it in
• unmagnetised