AC Circuits: Feynman's Physics Explained

Feynman Vol II9-10

The laws of electromagnetism let us analyze alternating-current circuits. For smoothly oscillating voltages and currents there is a beautiful trick using complex numbers: each component — resistor, capacitor, inductor — gets a complex 'impedance.' This turns the circuit's differential equations into simple algebra, making even complicated networks tractable. And resonance, so important in mechanics, shows up here all over again.

The big idea

Complex numbers turn messy AC circuits into simple algebra.

Think about it

How is an electrical circuit that 'rings' at one frequency like a mass bouncing on a spring?

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