There are three connections in a standard AC receptacle—the Hot wire, the Neutral wire and the Ground connection.

The Hot connection is, as the name implies, the one that carries the current and is usually at approximately 120 VAC (Volts AC) with respect to ground. (It is usually
the black wire on the gold terminal of the duplex outlet.)

The Neutral connection is the one that completes the path for the power from the Hot wire. It is usually the white wire on the silver terminal of the duplex outlet. This connection should be connected to ground at the distribution or circuit breaker box. NEVER DEPEND ON THIS CONNECTION TO BE A GROUND. This wire is, at best, “grounded” but can develop a significant voltage with respect to ground for a number of reasons.

The Ground connection is actually connected to the ground in a properly configured installation. Testing this connection should always be done before depending on it.

Testing should be done in the following manner:

1. Using a multimeter and INSULATED probe, set the meter to the 120 (or more) AC voltage range and connect the probes to the ground connector and a good earth ground such as a cold water pipe or other clear and confirmed ground. You should be able to adjust the meter range down to its lowest reading and not see any voltage at all. If you see any voltage reading that is stable, the ground is not up to the National Electrical Code and a licensed electrician should be called in to remedy the situation.
2. If you do not see a voltage, set the meter to read resistance and check the resistance reading. It should be less than 2 ohms. If not, there is a problem that needs to be rectified by a licensed electrician. NOTE: Do not attempt this step if the reading in step 1 shows any voltage or you will damage your meter!