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(* Indicates NEC 2011 Article 100 Definitions)

Arc - Electrons crossing a small gap between two conductors. An arc is likely occurring when a crackling noise is heard inside a device.

Arc Fault - An abnormal condition where an arc occurs (corroded or loose connection).

Arc fault circuit interrupter (AFCI) – A circuit breaker that will also trip when it detects an abnormal arc.

Arc flash - Happens when anything connected to a hot phase (like a hot wire) in the process of touching anything that is connected to a different hot phase, neutral or ground. The arc flash actually starts before contact is made when the current jumps a tiny gap.

Alternating current (AC) – Current that travels in both directions. Residential and commercial power use AC.

Amp - (Short for amperes) Electrical measurement of the quantity of the flow of electrons.

Ampacity* - The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

AWG - American wire gauge, a standard wire gauge system to correlate wire diameters to gauge numbers.

Circuit - Circuit breaker(s), conductors (wires), and electrical outlets. Conductors in a circuit contain hot, neutral, and ground conductor(s). Older systems may not contain ground conductors.

Electrical Definitions

Circuit breaker* - A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating. (The circuit breaker will trip during a short circuit, ground fault, and overload condition.)

Conductor – Materials that allow the flow of electrons easily, including silver, copper, gold, and aluminum. Electrical wires are mostly made of copper, some are made of aluminum.

Continuity - A circuit has continuity when there is a continuous path for electricity to flow through the circuit (free from open circuit conditions). A multimeter, continuity tester, and certain solenoid testers can measure continuity.

Continuous load - A load where the maximum current is expected to continue for three hours or more.

Current – The flow of electrons through a conductor, the quantity is measured in amps (A).

Current flow direction - It is not known for sure what direction currents flows. The conventional theory of current flow is from positive (+) to negative (-).

Dedicated circuit - A circuit that has only one receptacle and is used for one load that has a high current rating.

Device* - A unit of an electrical system that carries or controls (but does not use) electric energy as its principal function. (Example:  receptacle or switch)

Direct current (DC) - Current that only goes in one direction. Battery supplied power is DC.

Electrical load - Electrical equipment (appliances, electronics, light bulbs, etc.) that use electrical energy.

Electrical system - The electrical components used to supply electricity to a structure. Components include panels, wiring, outlets, fixtures, etc.

Fault - (Ground fault) This happens when an ungrounded conductor (hot wire) comes in contact with anything that is grounded (i.e. motor winding touching case, or hot wire of appliance touching the metal frame.)

Ground - An electrical reference point that connects to the earth. Ground connects to neutral at a single neutral point on an electrical system measuring zero volts (0 volts).

Ground conductor - Also known as grounding conductor, is connected to earth ground, and does not carry current during normal conditions. It connects to neutral at the grounding point of an electrical system. A grounding conductor will carry current during a short circuit or ground fault condition.

Ground fault – This happens when an ungrounded conductor (hot wire) comes in contact with anything that is grounded, (i.e. motor winding touching case, or hot wire of appliance touching the metal frame.)

Ground fault interrupter (GFCI) - A receptacle or circuit breaker that will trip when current from the hot does not return through the neutral (ground fault).

Ground screw - A green screw specifically used to connect a ground wire to a metal electrical box.

Gauge - See AWG.

Hot conductor – The ungrounded conductor. This is the conductor that has voltage. In a household, the wire color is black or red.

Impedance - Electrical measurement of the opposition of the flow of electrons in a conductor with the effects of capacitance and induction as measured in ohms.

Insulator - Materials that resist the flow of electrons, including plastic, fiberglass, and rubber.

Kilowatt - 1,000 watts

Kilowatt Hour (kWh) - 1,000 watts for 1 hour.

Line - (Electrical line) source of electrical power (electrical panel, circuit breaker).

Line Side - The wire connection terminals of a GFCI, occupancy sensor, photocell, etc. that connect to a circuit breaker through a wire.

Load - (Electrical load) Electrical equipment (appliances, electronics, light fixtures, etc.) that use electrical energy.

Load Side - The wire connection terminals of a GFCI, occupancy sensor, photocell, etc. that connect to a load.

NEC – National Electrical Code.

Neutral Conductor - Is a conductor that carries current in normal conditions. It is connected to ground at the neutral point in the system. The voltage on a neutral conductor is 0 volts (or very close to 0 volts under load conditions). Warning: A neutral conductor can carry voltage when opened on a live circuit.

Neutral point - Is where ground and neutral are connected in an electrical system.

NM Cable - Non-metallic cable commonly used for indoor residential wiring. NM cable contains one or two hot wires, a neutral wire, and a ground wire. A 12-3 NM cable contains four 12 gauge wires, two hot wires (black and red), one neutral wire (white), and one ground wire (bare).

Nominal voltage - 120 volts & 240 volts are the standard numbers assigned to designate a voltage class for residential. All those other voltages, 110 V, 115 V, 125 V, 130 V, 220 V, 230 V, 250 V, are high or low voltage ratings of equipment, bulbs, appliances, etc.

Higher voltage ratings are for switches, receptacles, bulbs, and certain loads. These ratings indicate the upper limit of voltage for a device or load to operate properly under normal conditions.

Lower voltage ratings are for loads (appliances, motors). These ratings indicate the lower limit of voltage to operate properly under normal conditions.

Ohms -  Electrical measurement of the opposition of the flow of electrons in a conductor.

Open circuit - An opening in a conductor path that prevents the normal flow of electricity.

Outlet - The points at which the electrical system are accessed. (Receptacle outlet, lighting outlet, etc.)

Overcurrent* -  Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit, or ground fault.

Overload* – Operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated ampacity that, when it persists for a sufficient length of time, would cause damage or dangerous overheating. A fault, such as a short circuit or ground fault, is not an overload.

Photocell - A switch that will close when darkness falls, usually turning on lights at night.

Potential difference - The difference between positive and negative charges; these differences result in voltage.

Power - Electrical measurement of The total electrical energy including voltage (force) times current (quantity). Power is measured in watts (W).

Qualified person* - One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved.

Resistance - The opposition of the flow of electrons in a conductor as measured in ohms.

Short circuit - An abnormal condition where a hot conductor comes in contact with neutral, ground, or another hot conductor of a different phase.

Volts - Electrical measurement of force or potential difference.

Voltage – The electrical force or potential difference measured in volts (V).

Voltage (Nominal) - See Nominal Voltage.

Voltage Drop - The drop in voltage from the voltage source to a load caused by resistance in a circuit path (mostly wires).

Volt-amps (VA) is an electrical measurement of power (volt-amps = volts * amps * power factor). Volt-amps is known as apparent power.

Watts - Electrical measurement of power (volts x amps).

Wire Makeup - Two or more wires connected together with wire nuts inside an electrical box.