Basic Electrical Terms

Basic Electrical Terms

AC and DC: Abbreviations for alternating current and direct current respectively. 

Current - A movement of electricity analogous to the flow of a stream of water. 

Direct Current - An electric current flowing in one direction only (i.e. current produced 

using a battery). 

Alternating Current - a periodic electric current that reverses its direction at regular 

intervals. 

Accessible: Three common uses of accessible: (Wiring methods) - Capable of being removed 

or exposed without damaging the building structure of finish, or not permanently enclosed by 

such. Wires in concealed raceways are not considered accessible. (Equipment) -Admitting close 

approach; not guarded by locked doors or other effective means. 

Readily Accessible - Capable of being reached quickly for operation, renewal, or 

inspections without the requirement of climbing over or removing obstacles or use of 

portable ladders, chairs, etc. 

Amp or Ampere: The unit of intensity of electrical current (the measure of electrical flow), is 

abbreviated a or A. 

Box: An enclosure designed to provide access to the electrical wiring system. Uses include but 

are not limited to provide device and lighting outlets and wiring system junction points. Specially 

designed boxes are required for the support of listed ceiling fans weighing less than 35 lb (15. 

kg). Fans exceeding this weight limit must be supported independently of the outlet box. 

Circuit Breaker: A device designed to open and close a circuit by non-automatic means and to 

open the circuit automatically on a predetermined over current without damaging itself when 

operated according to its rating. 

Circuit: A complete path from the energy source through conducting bodies and back to the 

energy source. 

Conductor: a substance or body capable of transmitting electricity. Bare - A conductor having 

no covering or electrical insulation whatsoever. 

Covered - A conductor encased within material of composition or thickness that is not 

recognized by the NEC as electrical insulation. 

Insulated - A conductor encased within material of composition or thickness that is 

recognized by the NEC as electrical insulation. 

Device: A unit of an electrical system that is intended to carry but not utilize electricity. 

Equipment: A general term including material, fittings, devices, alliances, fixtures, apparatus, 

and similar items used as a part of, or in connection with, an electrical installation. 

Fuse: An over current protective device with a circuit opening part that is heated and broken by 

the passage of an over current through it.

GFCI (Ground Fault Circuit Interrupter): A device intended for the protection of personnel that 

de-energizes a circuit or portion of a circuit when the current to ground exceeds a preset value. 

"Ground Fault" is the name applied to this undesired circuit condition. In dwelling units (e.g. 

houses, apartments), GFCI protection is currently required in bathrooms, garages, outdoors, 

unfinished basements, kitchens and wet bar sinks. Other specific installations and/or areas may 

also necessitate the need for protection 

Ground: A conducting connection, intentional or accidental, between an electrical circuit or 

equipment and the earth, or some conducting body that serves in place of the earth. Other 

associated terms are: Grounded conductor - A system or circuit conductor that is intentionally 

connected to ground. This conductor has also been referred to as the neutral or common 

conductor. Grounding conductor - a conductor used to connect equipment or the grounded 

circuit of a wiring system to the grounding electrode (s). Ungrounded conductor - A current 

carrying conductor not connected to ground. 

Kilowatt-hour: Work done at the steady rate equivalent to 1000 watts in one hour. Power utility 

companies’ base their billing upon the number of kilowatt-hours (KWH) consumed. 

Labeled: Equipment or materials that a label or other identifying mark of a listing organization 

has been attached. 

Lamp: A general term for various devices for artificially producing light. 

Listed: Equipment and/or materials included in a list published by an organization concerned 

with product evaluation and production of listed items. The listing states whether the item meets 

designated standards or is suitable for use in a specified manner. Listing organizations 

acceptable to jurisdiction authorities include Underwriters' Laboratories (UL) and CSA. 

NEC (National Electrical Code): a document produced by the National Fire Protection 

Association for the purpose of the practical safeguarding of persons and property from hazards 

arising from the use of electricity. Authorities having legal jurisdiction over electrical installations 

adopt the code for mandatory application ( i.e. incorporate the code into law). 

Ohm: The unit of electrical resistance and impedance, abbreviated with the symbol omega, W. 

Resistance is the opposition offered by a substance to the passage of electrical current. 

Impedance is the apparent resistance in a circuit to the flow of alternating current. 

Ohm's Law: A statement of the relationship, discovered by the German scientist G. S. Ohm, 

between the voltage, amperage and resistance of a circuit. It states the voltage of a circuit in 

volts is equal to the product of the amperage in amperes and the resistance in ohms. E=IR

Over current: Any current in excess of the rated current or ampacity. It may result from 

overload, short circuit or ground fault. 

Overload: Operation in excess of normal full-load rating or rated ampacity which could cause 

damage or dangerous overheating if continued for a sufficient time. A fault, such as a short circuit 

or ground fault, is not an overload. See "Over Current".