Electrical current is the flow of charged particles and more specifically, for this discussion, the flow of electrons on a wire. In the late 19th century, Nikola Tesla defeated Thomas Edison in the battle for the soul of electric current. Edison held many patents for direct current (DC) and fought hard to make it the standard, but ultimately the much more flexible alternating current (AC), favored by Tesla, won out. Not only is AC current much easier to transport long distances, it is the safest of the two options by far.

Direct current is constant and moves in one direction. Alternating current moves back and forth, positive to negative, and back again. If you look at a graph of each, you’ll notice that DC requires a constant voltage to move the electrons along. AC on the other hand, is moved by a voltage that oscillates between two points. Notably, with AC, the voltage crosses the zero point once each cycle. This is critical because at that moment when the voltage is at zero, there is no current. With a DC system the current is always on. This is especially problematic when there is a fault or break in a DC electrical system, since the current is always flowing, it can jump the break and start a fire.