Definitions of Terms Related to Electricity

Ampere—The unit for measuring intensity of flow of electricity. Its symbol is “I.”

Bonding—Applies inert material to metal surfaces to eliminate electrical potential between metal components and prevent components and piping systems from having an elevated voltage potential.

Circuit—The flow of electricity through two or more wires from the supply source to one or more outlets and back to the source.

Circuit breaker—A safety device used to break the flow of electricity by opening the circuit automatically in the event of overloading or used to open or close the circuit manually.

Conductor—Any substance capable of conveying an electric current. In the home, copper wire is usually used.

• A bare conductor is one with no insulation or covering.
• A covered conductor is one covered with one or more layers of insulation.

Conductor gauge—A numeric system used to label electric conductor sizes, given in American Wire Gauge (AWG). The larger the AWG number, the smaller the wire size.

Current—The flow of electricity through a circuit.

• Alternating current is an electric current that reverses its direction of flow at regular intervals. For example, it would alternate 60 times every second in a 60-cycle system. This type of power is commonly found in homes.
• Direct current is an electric current flowing in one direction. This type of current is not commonly found in today’s homes.

Electricity—Energy that can be used to run household appliances; it can produce light and heat, shocks, and numerous other effects.

Fuse—A safety device that cuts off the flow of electricity when the current flowing through the fuse exceeds its rated capacity.

Ground—To connect with the earth, as to ground an electric wire directly to the earth or indirectly through a water pipe or some other conductor. Usually, a green-colored wire is used for grounding the whole electrical system to the earth. A copper wire is usually used to ground individual electrical components of the whole system. (The home inspector should never assume that insulation color wiring codes have been used appropriately.)

Ground fault circuit interrupter (GFCI)—A device intended to protect people from electric shock. It de-energizes a circuit or portion of a circuit within an established very brief period of time when a current to ground exceeds some predetermined value (less than that required to operate the over-current protected device of the supply circuit).

Hot wires—Those that carry the electric current or power to the load; they are usually black or red.

Insulator—A material that will not permit the passage of electricity.

Kilowatt-hour (KWH)—The amount of energy supplied y one kilowatt (1,000 watts) for 1 hour (3,600 seconds), equal to 3,600,000 joule. Electric bills are usually figured by the number of KWHs consumed.

Neutral wire—The third wire in a three-wire distribution circuit; it is usually white or light gray and is connected to the ground.

Resistance—A measure of the difficulty of electric current to pass through a given material; its unit is the ohm.

Service—The conductor and equipment for delivering energy from the electricity supply system to the wiring system of the premises.

Service drop—The overhead service connectors from the last pole or other aerial support to and including the splices, if any, connecting to the service entrance conductors at the building or other structure.

Service panel—Main panel or cabinet through which electricity is brought to the building and distributed. It contains the main disconnect switch and fuses or circuit breakers.

Short circuit—A break in the flow of electricity through a circuit due to the load caused by improper connection between hot and neutral wires.

Volt—The unit for measuring electrical pressure of force, which is known as electromotive force. Its symbol is E.”

Voltage drop—A voltage loss when wires carry current. The longer the cord, the greater the voltage drop.

Watt—The unit of electric power. Volts times amperes = watts.

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Source: National Center for Environmental Health