Reversed Polarity?

As a home inspector we find a verity of safety concerns, but one of the most common safety concerns is reversed wiring (reversed polarity) on receptacles. This is a potentially dangerous problem, but one that can be easily corrected. Here is a typical question I received on reversed polarity.

Question:
We are moving to New Castle because of a transfer. We went there and found a house we liked, but we had to leave before the Home Inspector could come. We received his report and everything looks good, but there was a note that some of the receptacles had reversed polarity. The report did not indicate that this is a big problem. Since I do not know what reversed polarity is and I have a fear of electricity, this concerns me.
Can you tell me what is reversed polarity and is it dangerous?
Can this condition be corrected?



Answer:
The wire that supplies the power to the outlets consists of three wires, a black wire a white wire and a non-insulated copper wire. The black wire is the hot wire. The white wire is a neutral, and the non-insulated copper wire is a ground. An outlet is wired with the hot connected to the side of the outlet with the small slot, and the neutral lead is connected to the bigger slot. This is done for safety reasons. Cords have one of the prongs wider so the neutral side and hot side line up correctly to match the wiring of the appliance. Provided the outlet is wired correctly, appliances are wired so the hot wire goes to the on and off switch. When wired this way, when the switch is off, there will be no voltage inside the device. If the outlet is wired in reverse (Reversed Polarity) this means that the hot is wired to the bigger slot and the neutral is wired to the smaller slot. With reversed polarity, now the on/off switch is opening and closing the neutral. This will turn the appliance on and off, but even in the off position the appliance still has electricity running through it. This could be a potential danger, but this is a very easy and inexpensive situation to have corrected.