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 ...

In contrast to alternating current, or AC, which, depending on the supply's frequency, switches direction 50 or 60 times per second, the current in DC circuits flows only in one direction.

Thomas Edison favored DC circuits, but Nikola Tesla thought AC circuits were the way to go. Clearly Tesla won that argument. Let’s see why!

To understand the difference between DC and AC, consider the flow of electrons in a wire. In a DC circuit, electrons move in one direction and keep rotating in the circuit.