Home Wiring and Electrical Glossary

Alternating current (AC) An electric current in which voltage flows in one direction one instant and in the opposite direction the next. The direction of current flow reverses at regularly recur ring intervals.

Ampacity How much current, expressed in amperes, a conductor can carry.

Ampere A measure of the amount of electric current flow.

Applied codes The most recently adopted NEC, plus locally required additions to the NEC, at the time of the work. Also known as Enforced Codes and Local Codes.

Approved Minimum standards established by an authority have been met.

Armored cable A flexible, metallic-sheathed cable used for indoor wiring, commonly called BX or Greenfield.

Ballast A magnetic coil that provides the starting voltage or stabilizes the current in a circuit (as of a fluorescent lamp).

Bonding The permanent adhesion of metallic parts, forming an electrically conductive path. See also Ground.

Box A device used to contain wire terminations where they connect to other wires, switches, or receptacles.

Branch circuit A circuit that supplies a number of receptacles for lights or appliances.

Burrs The rough edges caused when cutting conduit pipe.

Bus bar A rigid conductor at the main power source to which three or more circuits are connected.

BX See Armored cable. Cable A conductor consisting of two or more wires that are grouped together in an overall covering.

Chases Spaces inside finished walls and between floors used for running ductwork or vent pipes.

Circuit The complete path of an electric current, leading from a source (generator or battery) through components (for example, electric lights), and back to the source.

Circuit breaker An electro magnetic or thermal device for interrupting an electric circuit when the current exceeds a predetermined amount; can be reset.

Code, National Electrical (NEC) A set of rules sponsored by the National Fire Protection Association, under the auspices of the American National Standards Institute, to protect per sons, buildings, and their contents from dangers due to the use of electricity.

Color coding The identification of conductors by color.

Common ground connection Where two or more continuous grounded wires terminate.

Conductor A low-resistance material, such as copper wire, through which electricity flows easily.

Conduit Metal or plastic tubing used to enclose electrical conductors.

Connector, solderless A device (typically plastic insulated) that uses mechanical pressure rather than solder to establish a connection between two or more conductors; wire nut.

Continuity An uninterrupted electrical path.

Current The movement or flow of electricity; the time rate of electron flow, usually measured in amperes.

Cycle A complete positive and negative alternation of a current or voltage.

Device A unit or component that carries but doesn’t use current, such as a junction box or switch.

Direct current (DC) An electric current that isn't pulsed and flows in only one direction.

Double-taps Situations in which one fuse or breaker is used to protect two circuits.

Electric charge The electric energy of a body or particle. The electron has an inherent negative charge; the proton has an inherent positive charge.

Electric current The flow of electricity through a conductor.

Electron The negatively charged particle of an atom; also called negatron. The flow of electrons in a conductor is what constitutes electric current.

Exposed Wiring designed to be easily accessible.

Feeder The circuit conductors between the service equipment and the branch-circuit over- current device.

Fish tape Flat, steel spring wire with hooked ends, used to pull wires through conduits or walls.

Fitting An accessory (such as a bushing or locknut) used on wiring systems to perform a mechanical rather than electrical function.

Flexible cable A conductor made of several strands of small-diameter wire.

Four-way switch Used along with two 3-way switches to control one or more lights from three separate locations.

Fuse A safety device inserted in series with a conductor, containing metal that will melt when heat is produced by an excess current in the circuit, thereby breaking the circuit.

Ground A conducting connection between an electric circuit and the earth or some other conducting body.

Grounded Connected to the earth or some other conducting body. The grounded wire is always white.

Grounding conductor The wire (green or bare) in a cable that carries no current; used as a safety measure to establish a ground.

Ground fault A situation where electricity can flow outside the conductors intended to carry power: When a hot wire at a bare point, for example where connected to a receptacle, touches a grounded component, such as a conduit or a grounding wire.

Ground Fault Circuit Interrupter (GFCI) Sophisticated overcurrent device that detects minute leaks of power and then quickly disengages that circuit.

Hanger A metal or insulated strap used at intervals to support electrical cable between points of connection.

Hot wires The conductors of a house circuit that aren't grounded and are carrying power; any color but white or green.

Impedance The total opposition to alternating current by an electric circuit.

Insulation Nonconducting materials used to cover wires and in the construction of electrical devices.

Insulator A nonconductor that's used to support and isolate a conductor that carries current.

Inverter Electronic transformer capable of converting DC electricity into AC power at high levels of efficiency.

Junction box A box in which several conductors are joined together.

Kilowatt-hour (Kwh) The standard billing unit, equivalent to the energy transferred or ex pended in one hour by one kilo watt of power. Equals 1,000 watt- hours.

Knockout A die-cut impression in outlet and switch boxes so designed that it can readily be removed to provide an opening for access.

Lighting outlet An outlet al lowing the direct connection of a lamp holder, lighting fixture, or pendant cord ending in a lamp holder.

Live wire A wire that carries current; also called hot wire.

Lugs Clamping elements built in to electrical devices.

Meter, electric A device that measures how much electricity is used.

National Electrical Code See Code, National Electrical.

Neutral wire The conductor in a cable that's kept at zero voltage. All current that flows through the hot wire must also flow through the neutral wire.

Ohm The unit of resistance in a circuit or electrical device; equal to the resistance in a conductor in which one volt of potential difference produces a current of one ampere.

Open circuit An electric circuit with a physical break in the path (caused by opening a switch, disconnecting a wire, burning out a fuse, and so forth), through which no current can flow.

Outlet A metal or plastic box in which electrical wiring is connected to electrical components.

Overcurrent-protection device A fuse or circuit breaker that's used to prevent an excessive flow of current.

Overload Current demand exceeding that for which the circuit or equipment was designed.

Plug, attachment A device inserted in a receptacle to connect conductors of attached flexible cord and conductors that are permanently connected to the receptacle.

Polarity See Polarizing. Polarized plug A plug whose prongs are designed to enter a receptacle in only one orientation.

Polarizing Using color to identify wires throughout a system to ensure that hot wires will be connected only to hot wires and that neutral wires will run back to the ground terminals in continuous circuits.

Power The rate at which work is being done.

Raceway A channel that contains electrical conductors.

Receptacle A contact device in stalled at the outlet to supply current to a single appliance.

Resistance A property of an electrical conductor, measured in ohms, that resists the flow of current according to the atomic nature of the conductor. Conductors such as copper, silver, and aluminum offer little resistance; poor conductors, such as glass, wood, and paper, offer more resistance.

Romex® A trademark for one brand of NM cable (nonmetallic sheathed cable) used for indoor wiring.

SLB (Service LB) El-shaped conduit body with an opening on the back for wiring access, de signed to mount flush to a wall.

Screw terminal A means for connecting wiring to devices using a threaded screw.

Service conductors Electrical conductors that extend from the street main or transformer to the service equipment of the building being supplied with power.

Service equipment Electrical equipment located near the en trance of supply conductors that provides main control and enables cutoff (via fuses or circuit breaker) for the supply of current to the building.

Service panel The main panel through which electricity is brought from an outside source into a building and distributed to the branch circuits.

Short circuit An improper connection between hot wires or between a hot wire and a neutral wire.

Smart house An emerging technology in which computers are used to incorporate telecommunications, entertainment con soles, energy efficiency, and safety features into the electrical system of a home.

Solar photovoltaic systems Control and storage devices that convert sunlight into electricity.

Solar panels Slices or thin films of semiconductor material that are wired, assembled, and bonded to a suitable substrate to form a single panel of uniform size and optimum output.

Splice A connection made by joining two or more wires.

Split receptacle A dual receptacle in which each of the two outlets is connected to a different branch circuit rather than a common circuit.

Stranded wire A quantity of small cables that are twisted together to form a single conductor.

Switch A device used to connect and disconnect the flow of current or to divert current from one circuit to another; used only with hot wires, never with neutral or ground wires.

Symbols, electrical Lines, letters, and signs used on building plans to represent where wiring circuits, switches, receptacles, and other electrical features are located.

Three-way switch A switch having three different conductor terminals. Two such switches are needed to control a light from two separate locations.

Triplex Cabled assembly of two insulated conductors loosely wrapped around one bare conductor, commonly used in ser vice drops.

Two-way switch Used to control one or more lights or other electrical outlets from one location; also called single- pole switch.

Underwriter’s knot A knot used to tie two insulated conductors at the terminals inside an electrical plug; used to relieve strain on the terminal connection.

Underwriter’s label (UL label) A label applied to manufactured devices that have been tested for safety by Underwriters’ Laboratories and approved for placement on the market. These labs are supported by insurance companies, manufacturers, and other parties concerned with electrical safety.

Volt A unit of measurement for electrical pressure (comparable to pounds of pressure in a water system).

Voltage The electromotive force or potential difference between two points of a circuit, measured in volts, that causes electric current to flow. One volt creates a current of 1 ampere through a resistance of 1 ohm.

Voltage drop A loss of electric current caused by overloading wires or by using excessive lengths of undersized wire. Often indicated by dimming of lights and slowing down of motors.

Volt-ampere In an AC circuit, a unit of measurement of electric power equal to the product of volts times amperes. In DC power, 1 volt-ampere equals 1 watt; in AC it's a unit of apparent power.

Watt A unit of measurement of electric power. (Volts times amperes equals watts of electric energy used.) One watt used for 1 hour is 1 watt-hour; 1,000-watt hours equals 1 kilowatt-hour (the unit by which electricity is metered and sold by utility companies).

Wire An electrical conductor in the form of a slender rod or cable.

Wire gauge A standard numerical method of specifying the physical size of a conductor. The American Wire Gauge (AWG) series is most common.

Wire nut See Conductor, solderless.

Wiring diagram A drawing, in symbolic form, plotting conductors, devices, and connections.