Editor's Note: Here's another take on the transformerless AC line power supply, which finds use in some well-insulated, low-power devices. Our technical reviewer pointed out that C ac should be an ...

Alternating current (ac) or direct current (dc) circuits are capable of carrying very different currents, as illustrated by the ratings on the switch in Figure 1.This is why it’s so important ...

The more typical unit of energy for ac power circuits is watt-hours, Wh. In this case, t is in hours. If P is in kilowatts, kW, and t is in hours, J has units of kilowatt-hours, kWh.