See the cause
Move a magnet near a conducting coil
Pole facing the coil
Motion of the magnet
The meter direction uses the wiring shown; reversing the pole reverses the deflection.Current flows only while the flux linkage changes.
Flux-linkage magnitudepredict first
Induced emfpredict first
Coil’s force on magnetpredict first
Follow one rotation
Flux linkage and induced emf
The green marker shows NΦ; the copper marker shows induced emf at the same angle.Slow-motion animation
Flux linkage, NΦ0.400 Wb turns
Instantaneous emf0.00 V
Peak emf12.6 V
Exam bridge: Faraday’s law and Lenz’s law
ε = − d(NΦ) / dtMagnitude comes from the rate of change. The minus sign supplies the opposing direction.
Read the equation as a sentence
- No change in flux linkage means no induced emf.
- A faster change, a stronger field or more turns produces a larger emf.
- The induced current produces its own magnetic effect that opposes the change in flux linkage.
Magnet mode is a qualitative closed-circuit model, so it compares relative emf rather than claiming a voltage for an unspecified magnet. Rotating-coil mode uses a uniform field, A = 0.010 m² and the displayed ideal generator equations.