Ampere (Amp): Unit used in measuring electrical current, based on the number of electrons flowing past a given point per second. Many elements of a wiring system are rated in amperes for the greatest of a wiring system are rated in amperes for the greatest amount of current they can safely carry.
Alternating Current: Abbreviated as AC. Electrical flow that cycles or reverses direction-60 or so times per second (in the case of “60-hertz” current).
Ampacity: Coined word combining ampere and capacity. Expresses in amperes the current-carrying capacity of electrical conductors.
Antioxidant: A paste applied to aluminum wires to inhibit corrosion and maintain safe connections.
Armored cable: Flexible cable, containing two or more wires, with a protective metal sheathing.
Ballast: Transformer that steps up the voltage in a fluorescent lamp.
Bell wire: A thin wire used for doorbells. Typically 18-gauge.
Bimetal: Two metals that expand and contract at different rated to open or close a circuit automatically. They are commonly used in circuit breakers and thermostats.
Bonding: connecting metal components of an electrical system to form a continuous conductive path capable of handling any current likely to flow.
Box: A metal or plastic container with openings for cable. All electrical connections must be made inside a code-approved electrical box.
Branch Circuit: Any one of many separate circuits distributing electricity throughout a house from the last over-current device protecting the circuit.
Bus bar: A long terminal inside a service panel. Circuit breakers or fuses connect to hot bus bars; neutral and ground wires connect to neutral and grounding bus bars. Some service panels have separate bus bars for neutral and ground wires (required in Canada), while others have only one neutral/ground bus bar.
BX cable: Armored cable containing insulated wires and no ground wire; the sheathing acts as the grounding path.
Cable: Two or more insulated wires wrapped in metal or plastic sheathing.
Candela: The unit of luminous intensity emitted in a specific direction by a source equal to one lumen per steradian – the unit of solid angle that, having its vertex in the center of a sphere, cuts off an area of the surface of the sphere equal to that the center of a sphere, cuts off an area of the surface of the sphere equal to that of a square with sides of length equal to the radius of the sphere. (There are four steradians in a sphere).
Circuit: Two or more wires carrying power from the service panel to devices, fixtures, and appliances and then back to the panel. Each circuit is protected by a circuit breaker or fuse in the service panel.
Circuit breaker: A protective device in a service panel that automatically shuts off power to its circuit when it senses a short circuit or overload.
Codes: Local regulations governing safe wiring practices.
Common terminal: On a three-way switch, the darker-colored terminal (often marked COM) to which the wire supplying power is connected.
Common wire: In a three-way switch setup, the wire that brings power to the switch or to the fixture.
Conductor: A carrier of electricity-usually, a wire.
Conduit: Plastic or metal pipe through which wires run.
Contemporary: upbeat, sophisticated design with modern contours for today's lifestyle.
Continuity tester: A device that tells whether a circuit is capable of carrying electricity.
Cord: Two or more insulated stranded wires encased in a flexible plastic or cloth sheathing.
Current: The flow of electrons through a conductor.
Device: Usually an electrical receptacle or switch.
Delayed-start tube: A type of florescent tube that takes a few seconds to warm up.
Derate: To lower total service capacity because not all the appliances and fixtures on a circuit are used at the same time.
Direct Current: Continuous flow from one electrical pole to another, as in a battery.
Duplex receptacle: the most common type of receptacle with tow outlets.
Electrical Metallic Tubing (EMT): Thin rigid metal conduit suitable for residential use.
End-line wiring: Also called switch-loop wiring. A method of wiring a switch, in which power runs to the fixture box. Compare through-switch wiring.
End-of-run: A receptacle at the end of a circuit.
Feed wire: The hot wire that brings power into a box.
Fixture: A light or fan that is permanently attached rather than being plugged into a receptacle.
Fish tape: A long strip of spring steel used for fishing cables and for pulling wires through conduit.
Flexible metal conduit: Tubing that can be bent easily by hand. See Greenfield.
Fluorescent tube: A light source that uses an ionization process to produce ultraviolet radiation. This becomes visible light when it hits the coated inner surface of the tub.
Footcandle: The unit measurement of luminance equal to one lumen per square feet; originally referring to a candle burning 1 foot away from a given surface.
Four-way switch: A switch used when a light is controlled by three or more switches.
Fuse: A safety device, located in a fuse box, which shuts off power when a circuit overloads.
Greenfield: Flexible metal conduit.
Ground: Wire or metal sheathing that provides an alternate path for current back to the service panel (and form there to a grounding rod sunk in the earth, or to a cold water pipe). Grounding protects against shock in case of an electrical malfunction.
Ground fault circuit interrupter (GFCI): A receptacle with a built-in safety feature, which shuts off when there is a risk of shock.
Grounding Electrode Conductor: Conductor that connects neutral bus bar of service panel to ground. Sometimes referred to as a “ground wire.”
Hardwired: An appliance that is wired via cable directly into a box rather than having a cord that plugs into a receptacle.
Hot Bus Bars: Solid metal bars connected to main power source in service panel and sub-panel. Branch circuit hot wires are connected to them.
Hot wire: The wire that carries power; it is either black or colored.
Impedance: The sum of resistance that’s found inside an electronic component like a speaker, for example. Measured in ohms.
Insulation: Material that does not carry current, such as the color coded thermoplastic insulation on wires.
Joist: Horizontal wooden framing member placed on edge, as in a floor or ceiling joist.
Jumper: Short piece of wire connected to the electrical box or to an electrical device, such as a switch or receptacle.
Junction box: An electrical box with no fixture or device attached; it is used to split a circuit into different branches.
Kelvin: The unit of absolute temperature used to designate the color temperature of a light source.
Kilowatt (kW): One thousand watts.
Kilowatt-Hour: Unit used for metering and selling electricity. One kilowatt-hour equals 1,000 watts used for one hour (or any equivalent, such as 500 watts used for two hours) (Kwh).
Knockout: A round slug or a tab that can be punched out to allow room for a cable or circuit breaker.
LB fitting: A pulling elbow made for outdoor use.
Lead: A wire (usually stranded) connected to a fixture.
Lumen: The unit measurement of luminous flux equal to the light emitted in a solid angle by a uniform point source of one candela intensity. So, basically, lux, lumen, footcandles and cendal are all pretty much the same thing. But Kelvin is way different.
Lux: The metric unit for measuring the amount of light that falls on an object. Lux is the European equivalent of the British footcandle (or lumen).
MC Cable: Armored cable with a ground wire in addition to at least two insulated wires.
Meter: A device used to measure the amount of electrical power being used.
Middle-of-run: A receptacle located between the service panel and another receptacle. Wires continue from its box to one or more other receptacle boxes.
Multi-tester: A tool that measures voltage of various levels, tests for continuity, and performs other tests.
National Electrical Code (NEC): The standard set of electrical codes for the US, updated every few years. Local codes sometimes vary from the NEC.
Neon tester: See Voltage tester.
Neutral Bus Bar: solid metal bar in service panel or sub-panel which provides a common terminal for all neutral wires. In service panel, neutral bus bar is bonded to metal cabinet and is in direct contact with earth through grounding electrode conductor. All neutral and grounding wires are connected to this bus bar. In sub-panel, only neutral wires are connected to neutral bus bar, which “floats” in metal cabinet (it is not bonded).
Neutral Wire: Grounded conductor that complete a circuit by providing a return path to the source. Except for a few switching situations, neutral wires must never be interrupted by a fuse, circuit breaker, or switch. Always identified by white or gray insulation.
Nonmetallic (NM) cable: Usually two or more insulated wires, plus a bare ground wire, enclosed in plastic sheathing. Older NM cable may have no ground wire and cloth rather than plastic sheathing.
OHM: The unit of measurement for electrical resistance or impedance.
Old-work box: See Remodel box.
Outdoor: Safe, romantic lighting made for enjoying every evening under the star.
Outlet: Any point in an electrical system where electricity may be used. Receptacles, fixtures, switches, and hardwired appliances are all outlets.
Overload: A dangerous condition caused when a circuit carries more amperage than it is designed to handle. Overloaded wires overheat. A circuit breaker or fuse protects wires from overheating.
Pigtail: A short length of wire spliced with two or more wires in a box and connected to a terminal so that two or more wires will not be attached to a terminal.
Plug: A male connection at the end of a cord designed to be inserted into a receptacle outlet.
Polarized plug: A plug with its neutral prong wider than the hot prong. It can be inserted into a receptacle outlet in only one way, thereby ensuring against reversing the hot and neutral sides of a circuit.
Raceway: Surface-mounted channels made of plastic or metal through which wires can be run to extend a circuit.
Receptacle: An electrical outlet into which a plug can be inserted.
Recessed can light: A light fixture that contains its own electrical box designed to be installed inside a ceiling so that its trim and perhaps lens is flush with the ceiling surface.
Remodel box: A metal or plastic electrical box that clamps to a wall surface (either plaster or drywall) rather than being fastened to framing. A remodel box must have an internal clamp to hold the cable.
Resistance: Property of an electric circuit that restricts the flow of current. Always measured in ohms.
Romex: A common name for nonmetallic cable.
Screw Terminal: Threaded screw found on sockets, switches, and receptacles; used to make wire connections.
Service Entrance Conductors: Wires connecting terminals of service entrance equipment to either the service drop (if service is overhead) or the service lateral (under ground service).
Service entrance: The point where power from the utility enters the house. A service entrance may be underground, or it may be at or near the roof.
Service panel: A large electrical box containing either fuses or circuit breakers. Power from the utility enters the service panel where it is divided up into branch circuits. Also called a panel box or main panel.
Short circuit: A dangerous condition that occurs when a hot wire touches a neutral wire, a ground wire, a metal box that is part of the ground system, or another hot wire.
Splice: To connect together the stripped ends of two or more wires usually by twisting them together and adding a wire nut.
Stripping: Removing insulation from wire or sheathing from cable.
Stud: Vertical wooden framing member; also referred to as a wall stud.
Sub-panel: A subsidiary service panel, containing circuit breakers or fuses and supplying a number of branch circuits. A sub-panel is itself controlled by the main service panel.
System ground: The method by which an entire electrical system is grounded. Usually a thick wire leading either to one or more rods sunk deep in the earth or to a cold-water pipe.
Three-way switch: A switch used when a light is controlled by two wiring.
Through-switch wiring: A method of wiring a switch, in which power runs to the switch box.
Traditional:classic, charming solutions that illuminate the most elegant homes.
Transitional:versatile, convenient and dependable lighting that enhances every living space.
Transformer: A device that reduces voltage usually from 120 volts to between 4 and 24 volts. Doorbells, thermostats, and low-voltage lights all use transformers.
Traveler wires: In a three-way switch setup, the two wires that run from switch to switch.
Type NM (Nonmetallic) Sheathed Cable: A multi-conductor cable, consisting of three or more wires that are contained within the same nonmetallic outer sheathing; used for interior wiring only.
Type UF (Underground Feeder) Cable: A multi-conductor cable, consisting of three or more wires that are contained within the same nonmetallic outer sheathing; used for exterior wiring only.
UL: Stands for Underwriters Laboratories, an independent agency that tests electrical products for safety. A UL listed item is approved for its intended use.
Underwriters knot: A special knot used to tie the wires in a lamp socket.
Volt (v): A measure of electrical pressure.
Voltage detector: A tool that senses electrical current even through insulation and sheathing.
Voltage tester: A tool that senses the presence of electrical current when its probes touch bare wire ends. Some voltage testers (often called voltmeters) also tell how many volts are present.
Watt (w): A measure of the amount of power that an electrical device, fixture, or appliance uses. Volts x amps = watts.
Wire nut: A plastic protective cap that screws onto two twisted-together wires to complete a splice.
Color Rendering Index: How to accurate colors appear, compared to the rendering ability of sunlight light, with a particular light bulb: generally a more important light quality measurement than color temperature. Outdoor light has CRI of 100, as does a 100-watt incandescent light bulb: the higher the number, the more accurate the CRI.
Cool: A bulb color that creates a more sterile glow. (Has nothing to do with the actual bulb temperature.
Efficacy: The ratio of light produced to energy consumed, or the number of lumens produced divided by the rate of electricity consumption.
Footcandle: A measurement of the illumination intensity expressed as the illumination produced by one lumen distributed over a 1-sqaure foot area.
Glare: Excessive brightness from a direct light Source: for example, a bright object in front of a dark background. Glare tends to affect older people more.
Kelvin Temperature: The color temperature of a light source. Yellow-red colors are considered warm; blue-green colors are considered cool. The higher the Kelvin, the cooler the light.Most consumer bulbs range from 2,00k to 6,500k. a 60-watt household incandescent bulb is 2,700k, giving it a soft, warm color. The higher the number, the whiter the light, but very high-Kelvin bulbs have a bluish- white light.
Life: Estimated time a light bulb will last.
Lumen: A measurement of light emitted by a bulb. A 100-watt incandescent emits 1750 lumens.
T: Diameter of a bulb. T12 means the bulb is 12/8 inches wide, or 1 in one half inches. Usually, you won’t be able to exchange one bulb size for another in a fixture with specific requirements.
Warm: A bulb color that appears with a soft white glow. (Has nothing to do with the actual bulb temperature.
Watt: The energy used by a light bulb.
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