Currents that swing back and forth, and the machines that make and use them.
Alternating current and the AC generator, instantaneous, mean and rms values, resistors, capacitors and inductors on AC with reactance and phase, impedance, the phasor method for CR, LR and LCR circuits, resonance and LC oscillations, average power and power factor, the choke coil, hot-wire meters, DC dynamos and motors, and transformers and power transmission.