Turning a coil
writes a sine wave
The same coil as the motor, driven the other way round: turn it by hand and it makes electricity. Flux through the loop follows a cosine as it rotates, and the EMF is that cosine's rate of change.
lawΦ = NBA cos ωt, so ε = NBAω sin ωt. Doubling the speed doubles both the frequency and the peak voltage.
tryWatch where the trace crosses zero against the coil's position.
noticeEMF is zero when the coil faces the field — maximum flux, but momentarily unchanging — and peaks when the coil lies edge-on.
in lifeEvery power station does this, at 50 or 60 turns a second, with steam or water turning the coil.
found byHippolyte Pixii built the first in 1832, a year after Faraday's discovery.