Electrical Polarity Testing

Domestic alternating current (AC) electrical circuits consist of two current-carrying conductors. One is positive or "hot" and has a constantly changing potential difference -- difference in electrical charge -- compared with the Earth, and the other is neutral or "cold" and has about the same potential difference as the Earth.

Reversed Polarity

Domestic appliances are designed to keep the positive conductor as far away from users as possible. Reversing the polarity -- that is, reversing the positive and neutral conductors -- significantly increase the risk of electric shock from an appliance.

Testing

Alternating current can be tested with a multimeter or volt ohm meter. Testing with a multimeter typically involves touching positive and negative leads from the meter to the wiring to be tested. A flashing negative sign ("-") before the numerical reading on the meter indicates that the polarity is incorrect.

Correction

If you find an outlet whose polarity is reversed, you should turn off your domestic electricity supply before inspecting the wiring. Positive wires, which are typically red or black, should be connected to the brass terminal, while neutral wires, which are typically white or gray, should be connected to the lighter-colored, chrome terminal.

References

• Galen Carol Audio: Determining Proper A/C Polarity