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.
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.
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.
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.
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.
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
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.
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.
Romex
service panel
subpanel
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.