The current that would not appear

Oersted had shown that electric current moves a compass needle. Michael Faraday wanted the reverse: could magnetism produce electricity? For years, a stationary magnet beside a wire gave him nothing.

In 1831 he wound two coils on an iron ring. Connecting one coil to a battery produced only a brief pulse in the other; disconnecting it produced another pulse in the opposite direction. The important thing was not magnetism alone. It was change.

Magnet approaches, meter deflects Scientific model diagram N N S S magnet approaches magnet approaches G G changing flux changing flux I = -0.000004746 A I = -0.000004746 A ℰ = −d(NΦᴮ)/dt, I = ℰ/R ℰ = −d(NΦᴮ)/dt, I = ℰ/R Ideal axial dipole and resistive circular coil Ideal axial dipole and resistive circular coil
magnet distance 0.2m flux linkage 18.96uWb induced EMF -0mV current 0uA Playback speed is adjusted; time readouts still show physical time.
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Diagram description

Animated physics diagram: faradays_induction; showing magnet distance, flux linkage, induced EMF, current.

Motion becomes current

Moving a magnet into a coil changes the magnetic flux and induces an electromotive force:

E=−dΦBdt.\mathcal{E}=-\frac{d\Phi_B}{dt}.

The minus sign expresses Lenz’s law: the induced current resists the change that produced it.

Faraday had little advanced mathematical training, but he thought in lines of force filling space. Generators, transformers, and motors grew from that physical imagination. The decade was not spent waiting for inspiration. It was spent learning that the failed stationary experiment had been asking the wrong question.