Reactance and AC theory
What capacitors and inductors do once the signal alternates.
CapacitanceStoring energy in an electric field.InductanceStoring energy in a magnetic field.Reactance and impedanceHow capacitors and inductors resist AC, and combine with resistance.Phasors and complex numbersThe maths that makes AC circuits tractable.Time constantsHow quickly RC and RL circuits charge and decay.Resonance and QTuned circuits, bandwidth and selectivity.TransformersTurns ratio, voltage, current and impedance transformation.Skin effect and RF resistanceWhy current crowds to the surface at high frequency.