CT Electrician key terms

The relationship stating that voltage equals current multiplied by resistance (E = I × R) in a resistive circuit; knowing any two of the three values lets you calculate the third.

The loss of voltage along conductors caused by their resistance and the current flowing through them; excessive drop can make equipment operate poorly or overheat.

The total opposition a circuit offers to alternating current, combining resistance with inductive and capacitive reactance; measured in ohms and used in fault-current and voltage-drop calculations.

The ratio of real power in watts to apparent power in volt-amperes in an AC circuit; a low value means more current is needed to deliver the same useful work.

A device that compares current leaving and returning on a circuit and opens the circuit quickly when a small imbalance shows current is leaking to ground, protecting people from shock.

A device that monitors the current waveform of a branch circuit and opens the circuit when it detects arcing signatures that could ignite surrounding materials.

The conductor that connects non-current-carrying metal parts of equipment to the grounding electrode system so fault current has a low-impedance path back to the source.

The circuit conductor intentionally connected to earth at the service, commonly called the neutral, which carries return current in a normally balanced circuit.

A conductor sized to ensure electrical continuity between metal parts that must be connected so they stay at the same potential and can carry fault current safely.

A fuse or circuit breaker that automatically opens a circuit when current exceeds its rating for a set time, protecting conductors and equipment from overheating.

The clear, unobstructed area required in front of electrical equipment, with minimum depth based on voltage and surrounding conditions, so a person can work safely.

The maximum continuous current, in amperes, that a conductor can carry under stated conditions of use without exceeding its temperature rating.

Reducing a conductor's allowable ampacity to account for conditions such as high ambient temperature or several current-carrying conductors bundled in one raceway.

The calculated volume required inside an outlet, device, or junction box to safely contain conductors, devices, fittings, and grounds based on conductor size and count.

Nonmetallic-sheathed cable with conductors rated 90 degrees C but used at the 60 degree C ampacity, common in dry interior residential wiring and marked by a plastic outer jacket.

A heavy-wall threaded steel or aluminum raceway that provides physical protection and can serve as an equipment grounding conductor when installed with listed fittings.

A support system of rails or troughs that carries and supports cables, allowing many conductors to be routed together and often used in commercial and industrial wiring.

A switch or device that opens all ungrounded conductors of a circuit or piece of equipment so it can be isolated from its power source for service or maintenance.

A device, such as a thermal overload relay, that protects a motor from sustained excess current caused by overload, overheating, or a stalled rotor.

A complete lighting unit consisting of the lamp or light source together with the housing, reflector, ballast or driver, and its connection to the branch circuit.

An assembly of circuit breakers or fusible switches mounted in a cabinet, fed by a main breaker or main lugs, that distributes power to branch circuits or feeders.

An area where fire or explosion hazards may exist because of flammable gases, vapors, dusts, fibers, or flyings present under normal or abnormal conditions.

A location where ignitable concentrations of flammable gases or vapors can exist during normal operations, or often because of repair or maintenance, requiring explosionproof wiring methods.

The portion of a health care building's wiring, including emergency and equipment branches, designed to supply critical patient care areas when the normal power source fails.

The array, inverters, conductors, and disconnects that convert sunlight into electrical energy and supply power either to a building or to the utility grid.

A fixed, stationary, or portable lighting unit used for advertising or display, containing a light source and related wiring, and subject to specific disconnect and grounding rules.

A system of circuits and equipment intended to supply illumination and power essential for life safety and health during a loss of the normal power source.

A permanently installed generator or other alternate source that supplies loads selected by the owner when normal power fails and is not required by code for life safety.

A circuit supplied from a source with limited power and voltage, such as a doorbell transformer output, that is considered low risk of fire or shock under normal conditions.

A circuit carrying voice, data, video, or similar signals between equipment, typically operating at low voltage and governed by rules separate from power wiring.

Cable listed for installation in air-handling spaces, made with low-smoke, low-flame-spread materials so a fire does not readily spread through the duct system.

The estimating process of counting and measuring materials, fixtures, and devices from drawings and specifications to build the job's material and labor list.

A written, signed amendment to a construction contract that modifies the scope, price, or schedule after the original agreement was executed.

The ratio on a drawing showing how a measured distance on the plan relates to the real distance on the project, such as one-quarter inch equals one foot.

A safety procedure in which an energy-isolating device is locked and tagged so equipment cannot be re-energized while someone is working on it.

The distance from energized equipment at which a person could receive a second-degree burn from an arc flash without wearing appropriate protective equipment.

Clothing and gear such as insulated gloves, arc-rated clothing, and eye protection worn to reduce injury from electrical, thermal, and physical hazards.

A Connecticut credential issued by the Department of Consumer Protection that authorizes the holder to bid, contract for, and perform unlimited electrical work with proper permits and supervision.