Alternating Currents

Alternating current

An alternating current (a.c.) varies sinusoidally with time, reversing direction each cycle:

$$I = I_0\sin(\omega t), \qquad V = V_0\sin(\omega t)$$

where $I_0$ and $V_0$ are the peak values and $\omega = 2\pi f$ is the angular frequency. The UK mains is $230\ \text{V}$ (r.m.s.) at $50\ \text{Hz}$.