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Physics · 4.5.2 Electromagnetic induction · Paper 6

Induction. Move it.

Move a bar magnet into and out of a coil and watch the galvanometer deflect. A changing magnetic field induces an EMF (Faraday). The faster you move, the more turns, and the stronger the magnet — the bigger the EMF.

0625 Topic 4.5.2 — Induction Faraday & Lenz Generator effect
Drag the magnet through the coil. The galvanometer deflects only while the magnet is moving.

Drag the magnet left/right through the coil to induce an EMF.

Variables

15
1.0
1.5

Live readouts

Magnet speed
0.0
Induced EMF
0.00 mV
Current direction
none
Coil turns N
15
EMF ∝ rate of change of flux. Stop moving → flux constant → no EMF. Reverse motion → reverse current (Lenz's law).
📋 Observations (Cambridge)
  • Moving the magnet in deflects the meter one way; pulling it out deflects it the other way.
  • Holding the magnet still inside the coil gives no deflection — induction needs a changing field.
  • Faster movement, a stronger magnet, or more turns all increase the induced EMF.
  • Reversing the poles reverses the induced current direction.
  • Lenz's law: the induced current opposes the change producing it.
🎯 Syllabus reference (0625)
  • 4.5.2 Electromagnetic induction — describe an experiment to show that a changing magnetic field can induce an EMF in a circuit; state the factors affecting the size of the induced EMF; state that the direction of the induced EMF opposes the change causing it (Lenz's law); relate to the a.c. generator.

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