🔄 AC Generator & Induction
📖 The Physics
Where does the electricity in the wall socket come from? Spin a coil in a magnetic field and the magnetic flux threading it keeps changing. By Faraday's law, a changing flux induces a voltage (EMF).
Because the flux varies smoothly as a cosine while the coil turns, the induced EMF comes out as a sine wave — this is exactly how power-station generators make alternating current (AC).
Φ = N·B·A·cos(ωt)
ε = −dΦ/dt = N·B·A·ω·sin(ωt), peak ε₀ = N·B·A·ω
Spin faster, use a stronger magnet, or add more turns and the peak voltage grows. The EMF is largest when the coil is parallel to the field (flux changing fastest) and zero when it is face-on.
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