Electrical and Lighting Glossary

By HomeAdvisor

Updated March 2, 2017

Overhanging light

A-Line Lamp:
An incandescent lamp generally used in most indoor residential homes.

Accent Lighting:
Lighting used to accent or highlight a particular object and is four or five times the level of ambient light in an area.

Alternating Current (AC) :
An electric current that changes direction with regular frequency.

An electric generator that produces alternating current.

Ambient Lighting:
Light that illuminates a space.

American Wire Gauge (AWG) :
A standard measure representing the size of a wire (a larger number represents a smaller wire).

The current a conductor can carry continuously.

A type of electric current that is produced by one volt applied across one ohm.

A unit of measure that utilizes varying physical restrictions.

Arc Tube:
A tube enclosed by a glass made of clear quartz that contains an arc stream.

An electrical device used with fluorescent lamps to supply sufficient voltage to operate the lamp but also then limits the current during operation.

Ballast Cycling:
An adverse condition where the ballast turns a lamp on and off due to overheating.

Two or more cells connected together to provide electrical current.

Blower Doors:
Devices used to see how much air leaks through windows, doors, and other places in a house.

Branch Circuit:
Conductors that protect circuits and outlets.

A reduction in power when the demand for electricity exceeds its generating ability.

BTU (British Thermal Unit) :
The standard unit for measuring heat quantities.

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Cable Lighting System:
A low voltage lighting system where electricity is conducted through cables.

Unit of light intensity in a specific direction, measured in “Candelas.”

A device that stores electrical charge.

An electrode that emits electrons.

A device that converts chemical energy into electrical current in a battery.

Circuit Breaker:
A device designed to open and close a circuit without causing damage to itself.

Circuit Extensions:
Items used to extend or add on to an existing circuit to provide an additional power source.

Code Corrections:
Procedures used to correct wiring that does not meet proper safety conditions.

Colored Glass Filter:
Glass formed with the color in the glass as opposed being coated on the surface.

Color Temperature:
A measure of the color appearance of a light source often described with terms such as “warm” (orange) or “cool” (white).

Compact Fluorescent Lamp (CFL) :
A family of small fluorescent lamps made with a glass tube design and high color illumination.

Constant Wattage (CW) Ballast:
A HID ballast where primary and secondary coils are isolated.

Continuous Load:
A load who’s maximum current is expected to continue for 3 hours or more.

The relationship between the illumination of an object and its background.

A device that serves to regulate the electric power delivered to a connected apparatus.

Cornice Lighting:
Light sources shielded by a panel parallel to the wall and attached to the ceiling.

Cove Lighting:
Light sources shielded by a recess and distribute light over the ceiling.

The flow of electricity measured in amperes.

Cut-off Angle:
The angle where a light fixture or other shielding device cuts off direct visibility of the lamp itself.

Daylight Compensation:
An energy-saving dimming system that reduces lamp output when in the presence of natural light.

Dispersed light distribution that softens illumination.

A device used to vary the brightness of lamps.

An electronic semiconductor device that allows a current to flow in just one direction.

Direct Current (DC) :
Circuit allowing electrons to flow in only one direction.

A light fixture recessed into the ceiling and illuminates in a downward direction.

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A measure used to compare light output to energy consumption.

A light source technology that provides long lamp life while still consuming very little energy.

Electric Resistance Heating:
A type of heating system that generates heat by passing current through a conductor, often used in baseboard heating systems.

Electromagnetic Interference: High frequency interference caused by electronic components that interfere with the operation of electrical equipment.

Emergency Lighting:
Lighting for when normal lighting fails.

The ability to do mechanical work; it is measured in kilowatt-hours.

Energy Efficiency Ratio (EER) :
The ratio of the cooling capacity of the air conditioner to the total electrical input in watts.

Energy-saving Ballast:
A magnetic ballast designed to operate more efficiently than “standard magnetic” ballasts.

A short circuit in an electrical system.

A tungsten wire that lights when electric current runs through it.

Flexible Track Lighting System:
A low-voltage lighting system where the track holding the light fixture is able to bend.

Fluorescent Lamps:
Devices that produce light by passing electricity through a gas.

The amount of light reaching an object.

Four-Way Switch:
A wall switch allowing three switches to control one lighting system.

The rate at which a current changes direction.

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Generator (Whole House or Portable):
A rotating machine that converts mechanical energy into electrical energy.

A condition caused by light coming directly into the eye from a light source.

An electrical distribution network.

A connection between an electrical circuit and the earth.

Halogen Lamp:
An incandescent lamp that contains halogen gases which slow the evaporation of the tungsten filament.

Hard Wired:
A light fixture permanently connected to an electrical source with a cord.

Hertz (Hz) :
The unit of frequency.

HID Lamp:
High Intensity Discharge lamps have a longer life and tend to provide more light than most light sources.

High Bay:
A type of lighting where the ceiling is 20 feet or higher.

High Output (HO) :
A lamp or ballast designed to operate at higher currents in order to produce more lumens.

High-Tech Troubleshooting:
A procedure used to identify any electrical problems.

A unit of power equal to 746 watts.

Hot Restart/Hot Restrike:
The automatic restarting of a HID light source after a momentary loss in power.

Illuminance (Light Level) :
The light incident on a surface.

A current’s surge.

Incandescent Light Bulbs:
Light bulbs that produce light by passing electricity through a thin filament.

Infrared Cameras:
Cameras used to see any heat leaking out of a building.

Infrared Radiation:
An invisible radiation where wavelengths are longer and lower than that of visible radiation.

Instant Start:
Fluorescent lamps that start instantly without pre-heating their cathodes.

Materials that have a high resistance to electrical currents.

A device that converts direct current into alternating current.

A positively or negatively charged atom or molecule.

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A unit of energy equal to one watt for one second.

Kilovolt (kV) :
A unit of electrical potential equal to 1,000 volts.

Kilowatt (kW) :
Real power delivered to a load.

A unit of energy equal to one kilowatt for one hour; the typical unit used to measure energy and for billing customers.

Layers of light in a given space that are created by several different kinds of lighting (a combination of task, general, ambient, and accent lighting systems, etc).

Light Emitting Diode: a small, energy-efficient electronic light that has a very long life.

Light Loss Factor (LLF) :
Factors that allow a lighting system to operate at less than initial conditions.

Light Trespass/Spill Light:
Light emitted into an unintended area.

Life Cycle Cost:
Total costs associated with purchasing and operating a system over its lifetime.

Limit Switch:
A switch used to alter the electric circuit.

Liquid-Filled Transformer:
A transformer immersed in a liquid that acts as both a cooling and insulating method.

Live Parts:
Electric components that are uninsulated or exposed and are therefore hazardous.

The amount of power supplied by an electrical device.

Disconnecting a load without damage.

Load Center:
The source for all power to a structure.

Load Curve:
A way to plot the electronic demand versus time.

Load Factor:
Measures how efficiently an electrical system’s capacity is utilized.

Load Switching:
Transferring a load from one source to another.

A screen made of opaque material to minimize glare from a light source.

Low Voltage:
A wiring system that provides power to an electronic device operating on a voltage level lower than the standard 110 volts.

A unit of measure used to describe the amount of light a lamp emits.

A light fixture.

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Mercury Vapor Lamp:
A HID lamp where light is produced by radiation from mercury vapor.

Metal Enclosed/Metalclad:
A device that is surrounded by a metal casing.

Metal Halide:
A HID lamp where the light is produced by radiation of metal halide and mercury vapors.

Electronic device used to move, switch, or adjust one or more of the systems within a dwelling.

National Electrical Code (NEC) :
A guideline used for safeguarding people/property from electrical hazards.

A silvery metal used to make purple glass for incandescent light bulbs, eye protection goggles, laser rods, filters, and lenses.

Occupancy Sensor:
Control device that turns lights off after a space becomes unoccupied.

The unit used for measuring resistance.

A material that does not transmit visible light.

The components of a light fixture; the light emitting performance of a fixture.

Where a current is taken to supply something outside the wiring system.

The excess of normal capacity that could cause damage due to overheating.

A voltage that is above the normal rated voltage for a circuit.

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PAR Lamp:
A parabolic aluminized reflector lamp.

Lamps equipped with shades to avoid glare that are suspended from the ceiling.

Classification of an AC circuit.

A light-sensing device that controls light fixtures and dimmers in response to detected light levels.

The rate at which energy is transferred.

Power Outage:
An interruption in power.

Power Outlet:
An assembly intended to distribute power to temporary equipment.

A ballast that uses a starter to heat up a fluorescent lamp before high voltage starts it.

A disruptive discharge that occurs in a solid dielectric.

Radio Frequency Interference (RFI) :
Interference to a radio frequency band caused by other high frequency equipment in the area.

Rapid Start:
A fluorescent system that does not require starters and emits light very quickly.

Rated Life:
The time at which half of a certain kind of lamp will burn out.

Reactive Power:
The product of voltage and current consumed by reactive loads.

Real (Active) Power:
The rate at which energy is transferred, often measured in watts or kilowatts.

Power sources in a structure that provide electricity.

The device on a light fixture that shrouds the lamp and redirects the light emitted from it.

The ballast’s ability to hold a constant output despite fluctuations in voltage.

A device that switches a load on or off due to small changes in its current.

Anything that limits a current’s flow.

Upgrading a preexisting fixture by installing new parts.

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A light fixture attached to a wall.

Light reflection characteristics of a material.

Equipment used for delivering electric energy from a utility to a wiring system.

Series Gap:
Internal gap(s) where voltage is supposed to appear.

The winding of two coils that are connected for series/multiple operation.

Service Cable:
Conductors transferred by cables.

Spacing Criterion:
The maximum distance that interior fixtures may be spaced to ensure uniform illumination.

A mirrored or polished surface.

An electrical device used to start a fluorescent lamp.

Stroboscopic Effect:
When rotating machinery appears to be standing still due to the alternating current supplied to multiple light sources.

A large assembly of panels mounted with protective devices.

Circuit interruption devices that control the flow of electricity in the home.

The normal flow of current.

Systems Capacity:
A system that has met a customer’s need.

A connection made from outside the wiring system.

Tandem Wiring:
An option where a ballast is shared by two or more luminaries, thereby increasing efficiency.

Task Lighting:
Lighting that is specifically installed to illuminate an area where tasks are performed.

Three-Way Switch:
A wall switch allowing two switches to control one lighting system.

Track and Accent Lighting:
A lighting system that provides variable degrees of light in multiple directions.

Transfer Switch:
An electronic device that can disconnect from one power source in order to connect to another.

A device wherein electromagnetic induction transfers electrical energy from one circuit to another.

A high amplitude, short duration pulse overlaid onto the normal voltage.

A material through which some light is transmitted but causes some distortion.

A material that transmits visible light with very little distortion.

A recessed light fixture that uses fluorescent lamps and is installed flush with the ceiling.

Turn Ratio:
The number of turns in a high voltage winding in relation to that of a low voltage winding.

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Underwriters Laboratories, Inc: a not-for-profit safety organization.

Uninterruptible Power Supply:
A device that provides a constant output in spite of interruption.

Light directed from a light fixture at or above 90 degrees.

UV Radiation:
Light that is invisible to the eye.

Fixtures with break-resistant shielding and tamper-proof screws.

Vapor-Tight Luminaire:
A light fixture that doesn’t allow water vapor or gas to enter its enclosure.

Visual Comfort Probability: a rating system for evaluating direct glare.

Very High Output (VHO) :
A fluorescent lamp operating at a very high current and therefore creating more light than a standard lamp.

An electrical flow that carries a current of one ampere.

Voltage Drop:
The loss of voltage due to electrical resistance of a wire and its light fixture.

Wall Grazing:
Dramatic light and shadow effects on a surface.

Wall Washing:
A special lighting method that produces an even level of light on a wall in order to reduce the surface’s texture.

A unit of power equal to one ampere.

A distribution network conducting electricity throughout a building.

Whole-House Fan:
A fan used to ventilate an entire building.

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