AK Electrician key terms

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

The relationship that electrical power in watts equals voltage multiplied by current (P = E × I). Used to size circuits and determine load in amperes.

The loss of voltage along conductors caused by their resistance as current flows. Excessive drop reduces equipment performance and is limited by code for feeders and branch circuits.

Current that periodically reverses direction, typically 60 hertz in North America. Most building wiring and motors operate on AC power.

The ratio of real power to apparent power in an AC circuit, expressed between zero and one. Low power factor means more current is drawn for the same useful work.

A power distribution method using three conductors with voltages offset by 120 degrees. It supplies large motors and commercial services more efficiently than single-phase systems.

A circuit where current has only one path through all components. The same current flows through each device and total resistance is the sum of individual resistances.

A circuit where current divides among multiple paths connected across the same voltage. Total resistance is always less than the smallest individual branch resistance.

The circuit conductors between the final overcurrent device protecting the circuit and the outlet or outlets it serves. It supplies the actual loads in a building.

All circuit conductors between the service equipment, source of a separately derived system, or other supply source and the final branch-circuit overcurrent device.

The conductors that carry power from the utility supply point to the service equipment disconnecting means. They are sized for the total calculated load of the premises.

The ratio of the maximum demand on a system to the total connected load. It allows feeders and services to be sized smaller than the sum of all loads.

The sum of the rated capacities of all equipment and outlets connected to a system. It is the starting point before demand factors are applied.

The maximum current a conductor can carry continuously under the conditions of use without exceeding its temperature rating. It depends on conductor size, insulation, and ambient conditions.

The reduction of a conductor's current-carrying capacity to account for bundling, high ambient temperature, or installation in thermal insulation. Tables and correction factors are applied.

A material, usually copper or aluminum, that carries electric current. Conductors are sized by cross-sectional area and identified by American Wire Gauge or kcmil.

The maximum temperature and voltage a conductor's covering is designed to withstand, such as 60, 75, or 90 degrees Celsius. It limits the ampacity permitted for the conductor.

A device such as a fuse or circuit breaker that automatically opens a circuit when current exceeds a safe level. It protects conductors and equipment from overheating.

The set of grounding electrodes, such as rods, pipes, or concrete-encased electrodes, and their bonding jumpers that connect the electrical system to earth.

The conductor that connects the non-current-carrying metal parts of equipment to the grounding system. It provides a low-impedance path for fault current.

The permanent joining of metal parts to form an electrically conductive path that ensures electrical continuity. Bonding keeps metal parts at the same potential to prevent shock.

A system that detects current leaking to ground and opens the circuit to prevent shock or fire. It is required for certain receptacles, equipment, and services.

A device that detects dangerous arcing in wiring and interrupts the circuit. It is required on many branch circuits in dwelling units to reduce fire risk.

The current a motor draws at its rated horsepower, voltage, and frequency under full load. It is taken from code tables rather than the motor nameplate for conductor sizing.

A device that protects a motor from sustained excess current that causes overheating. It is sized to the motor's nameplate current and is separate from short-circuit protection.

A means to disconnect the motor and controller from the power source for servicing. It must be within sight of the motor and controller unless specific exceptions apply.

Heating, ventilating, and air-conditioning units such as compressors, air handlers, and heat pumps. Their nameplates provide minimum circuit ampacity and maximum overcurrent protection values.

A channel of metal or nonmetallic material designed to hold and protect conductors, such as conduit or tubing. Raceways must be properly supported and have limited fill.

The percentage of a raceway's cross-sectional area occupied by conductors. Limits prevent overheating and make it possible to pull conductors without damage.

The required cubic-inch volume inside an outlet, junction, or device box to safely contain conductors, devices, and fittings. It is calculated from conductor counts and device allowances.

The process of shaping conduit into bends such as offsets, saddles, and 90-degree turns. Correct bending maintains a smooth raceway and keeps conductors from being damaged.

A box used to contain splices, receptacles, switches, or other devices at an outlet. It must be accessible and have adequate volume for the conductors it holds.

A contact device installed at an outlet for connecting a plug to the circuit. Its rating, grounding type, and location must match the circuit and code requirements.

A device that opens or closes a circuit to control the flow of current to a load. Switches must be rated for the circuit voltage and current they control.

The main switch or breaker used to disconnect all power from the service equipment. It must be readily accessible and clearly marked with its rating.

An area where fire or explosion hazards may exist due to flammable gases, vapors, dusts, or fibers. Equipment and wiring methods there must follow special classification rules.

A building or space with unique hazards or uses, such as health care facilities, places of assembly, or agricultural buildings. Wiring in these areas is subject to additional requirements.

Devices and materials approved for use in specific hazardous areas, marked with class, division or zone, and group. Using unapproved equipment there creates ignition risk.

A safety procedure that isolates energy sources and applies locks and tags before work begins. It prevents accidental energization of equipment being serviced.

An official authorization to perform electrical work, issued by the local authority before work starts. It documents the scope and triggers required inspections.

The review of electrical work by an authorized official to confirm it meets code and approved plans. Work must be accessible for inspection at required stages.

The organization or individual responsible for enforcing code requirements and approving equipment and installations. Local building officials commonly serve in this role.

A credential issued by the state that authorizes a business to offer and perform electrical contracting work. It requires a qualifying individual and compliance with state rules.

A state-issued credential allowing a person to perform electrical work under an electrical contractor. It is earned through experience, examination, and continuing requirements.

Required ongoing training hours that licensees complete to renew their electrical credential. It keeps practitioners current on code changes and safety practices.