AC vs. DC
4. Alternating Current (AC) vs. Direct Current (DC) and "hot" wires.
Now, let's talk about the difference between alternating current (AC) and direct current (DC). AC is the type of electricity that comes from your wall outlets. It changes direction many times per second (60 times in the US, which is 60 Hz). DC, on the other hand, flows in one direction only. Batteries are a common source of DC electricity. These fundamental differences affect how we think about "hot" wires.
In an AC circuit, the "hot" wire is constantly switching polarity, making it positive and negative in rapid succession. The neutral wire is supposed to be at or near ground potential, providing a return path for the current. However, due to the nature of AC power, the neutral wire can still carry current and, under fault conditions, can become energized. This is because the neutral isn't always perfectly at ground. There can be voltage drop along the neutral wire, which means its potential isn't zero all the way back to the source.
In a DC circuit, the positive wire is typically considered "hot" because it has a positive voltage relative to the negative wire. The negative wire serves as the return path. Ideally, the negative wire is at or near ground potential, but, as stated before, faults can occur that energize the negative wire. The critical thing to remember is that no matter if it's AC or DC electricity, both wires are part of a working circuit and need to be treated with the respect that potentially dangerous voltage is present.
Thinking about "hot" wires is really about understanding the potential difference between wires in a circuit. In both AC and DC systems, the potential for danger exists, and assuming a wire is harmless because of its color or function can be a mistake with severe consequences. As discussed, safe work practices, proper testing, and professional expertise are essential when dealing with electricity.
