Fluxion

Meet Fluxion, a wire loop who catches fewer field lines the more he tilts.

Magnetic flux measures how much magnetic field passes through a surface. It depends on the field strength B, the area A of the loop, and the angle θ between the field and the line perpendicular to the loop, Φ_B = BA cos θ. Its unit is the weber.

Take a square loop 20 cm on each side, with an area of 0.04 m², in a 0.5 T field. Facing the field straight on, θ = 0 and the flux is 0.5 × 0.04 = 0.02 Wb. Tilt it to 60° and the flux halves to 0.01 Wb. At 90°, edge on to the field, the flux is zero.

Faraday's law says that a changing flux drives a current around the loop. Spinning the loop keeps changing the angle, and so the flux.

That is exactly how a generator works, turning coils in a magnetic field to produce the alternating current that reaches our homes.