Common electrical terminology

ampacity

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

ampere

A type of electric current produced by one volt applied across a resistance of one ohm. It is also equal to the flow of one coulomb per second. Named after French physicist Andre M. Ampère 1836.

appliance

A non-lighting item that, by its resistance, consumes electricity rather than just passing it on.

arc fault circuit breakers

Electrical fires happen every day in the United States because of electrical shorts that produce intensely hot arcs. An arc fault circuit interrupter senses these arcs and stops them, making them smarter than traditional circuit breakers. Also known as a arc-fault interrupter, it will trip for line-to-neutral arcing whereas a standard circuit breaker will not.

branch circuit

The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).

breaker

An automatic switching device that disconnects power to a circuit when current or heat exceeds a certain level for a duration of time. It clips on to one or two live busbars in a panel box and passes electrical current through itself to the circuit wire attached to it. The three positions of a common breaker are: on, tripped (the middle position), and off.

breaker box

Otherwise known as a panel or panel box. It is a metal box in a building containing breakers for each electrical circuit. The "main" panel or "service" panel would be the central source for the home and would be receiving its power from the power company.

brownout

A reduction in voltage and/or power when demand for electricity exceeds generating capacity. The term brownout is misleading because customers generally do not notice the reduction, except when it affects sensitive electronic equipment.

buss bar

A piece of rigid metal within a panel or fusebox which distributes electricity to the various circuits. They're made up of thick strips of copper or aluminium that conduct electricity within a breaker box.

circuit breaker

A device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a pre-determined overcurrent without damage to itself when properly applied within its rating.

circuit extensions

To extend or add-on to an existing circuit to provide an additional power source.

code corrections

Procedure designed to eliminate wiring conditions that do not meet National Electrical Code requirements and safety conditions.

common

The terminal of a three-way switch (or the wire attached to it) which connects internally to either one or the other of the traveler terminals, depending on the position the switch is moved to.

continuous load

A load where the maximum current is expected to continue for 3 hours or more.

fault

A short circuit in an electrical system.

fuse

A legacy device that interrupts current to its circuit by melting apart. When tripped, the fuse is destroyed, opening the circuit. A tripped fuse must be replaced with a new one after the electrical fault or overload is located.

fuse box

Predecessor to the modern breaker box.

gang

Describes an accommodation of receptacles or switches in an electrical box.

ground

In residential wiring, the 3 wires are hot, neutral, and ground. Either not insulated or green insulated wire. The ground is the connection to the earth at the location of the electrical system. The ground wire is not connected so as to be part of the normal path of the circuit, as a neutral is. The earth ground only carries a current in a fault or short circuit condition and is a safety precaution.

ground wire

A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth. Being grounded means connected to earth or to some conducting body that serves in place of the earth.

harmonic

A multiple of the fundamental electrical frequency. Harmonics are present whenever the electrical power waveforms (voltage and current) are not pure sine waves.

high voltage

Voltage greater than 100,000 volts.

hot

In residential wiring, the 3 wires are hot, neutral, and ground. The black wire. The hot wire has voltage present and may be used to complete a circuit via the neutral, ground, or a human body standing on the ground.

IEC

International Electrotechnical Commission.

IEEE

Institute of Electrical and Electronics Engineers.

impedance

The total effects of a circuit that oppose the flow of an AC current consisting of inductance, capacitance, and resistance. It can be quantified in the units of ohms.

impulse

A current surge.

insulator

Any material which does not allow electrons to flow through it.

junction box

a box used only for making connections such as splicing into an electrical circuit.

kilowatt (kW)

Real power delivered to a load (W x 1,000 VA).

kilowatt-hour:

A unit of energy or work equal to one kilowatt for one hour. Abbreviated as kwh or KWH. This is the normal quantity used for metering and billing electricity customers. The price for a kwh varies from approximately 4 cents to 15 cents. At a 100% conversion efficiency, one kwh is equivalent to about 4 fluid ounces of gasoline, 3/16 pound LP, 3 cubic feet natural gas, or 1/4 pound coal.

megohmmeter

An instrument for measuring insulation resistance.

NEC

National Electrical Code.

NEMA

National Electrical Manufacturers Association.

neutral

In residential wiring, the 3 wires are hot, neutral, and ground. Neutral is the white wire. The junction point of the legs in a Wye circuit.

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.

panel

Otherwise known as a panel box or breaker box.

phase

Classification of an AC circuit usually single-phase, two wire or three wire; two-phase, three wire or four wire; or three-phase, three wire or four wire.

power

The rate at which work is performed or that energy is transferred. Electric power is commonly measured in watts or kilowatts. A power of 746 watts is equivalent to 1 horsepower.

real power

The rate at which work is performed or that energy is transferred. Electric power is commonly measured in watts or kilowatts. The term real power is often used in place of the term power alone to differentiate from reactive power. Also called active power.

Scotchlok

Insulation displacement connectors also known as a wire nut.

subpanel

The main breaker box or panel in a building is the central source for receiving power from the utility provider. A subpanel is another breaker box fed from the main breaker box panel.

transfer switch

An electronic device that under certain conditions will disconnect from one power source and connect to another power source.

volt

The electrical potential difference or pressure across a one ohm resistance carrying a current of one ampere. Named after Italian physicist Count Alessandro Volta 1745-1827.

volt ampere

A unit of apparent power equal to the mathematical product of a circuit voltage and amperes. Here, apparent power is in contrast to real power. On ac systems the voltage and current will not be in phase if reactive power is being transmitted. Usually abbreviated VA.

watt

A unit of power equal to the rate of work represented by a current of one ampere under a pressure of one volt. Named after the Scottish engineer James Watt, 1819.