EEA Electrician Exam key terms

The fixed relationship among voltage, current, and resistance in a circuit, expressed as voltage equals current times resistance. Knowing any two values lets you calculate the third, which underlies nearly every circuit calculation on the exam.

The loss of potential along conductors caused by their resistance and reactance as current flows. Excessive drop leaves equipment with insufficient voltage, so the exam tests both the calculation method and commonly applied limits for feeders and branch circuits.

The ratio of real power in watts to apparent power in volt-amperes in an alternating-current circuit. A low value means more current flows for the same useful work, which affects conductor and service sizing for motor and lighting loads.

The total power delivered to an alternating-current load, measured in volt-amperes and equal to voltage times current without regard to phase angle. Equipment such as transformers and generators is rated in these units because their capacity limits are thermal.

The total opposition a circuit offers to alternating current, combining resistance with inductive and capacitive reactance. It governs available fault current and voltage drop in alternating-current systems, so it appears in short-circuit and feeder calculations.

The maximum continuous current a conductor can carry under stated conditions without exceeding its temperature rating. Tables list base values, and correction and adjustment factors reduce them for high ambient temperature or multiple conductors sharing a raceway.

The reduction applied to a conductor's table ampacity when several current-carrying conductors share a raceway or cable, because bundled conductors cannot shed heat as freely. The number of conductors determines the percentage applied.

A multiplier applied to a conductor's table ampacity when the surrounding air is hotter or colder than the table's assumed conditions. Hotter surroundings reduce allowable current because the insulation reaches its limit sooner.

The temperature limit marked on lugs and equipment terminals, commonly 60, 75, or 75 degrees Celsius. Final conductor ampacity cannot exceed the lowest-rated termination in the circuit, which often controls the permitted size.

The percentage of a conduit's internal cross-sectional area occupied by conductors. Limits keep conductors from binding during installation and from overheating, and the permitted percentage depends on whether one, two, or three or more conductors are present.

The minimum curve a cable or conduit may be formed into without damaging insulation, shielding, or the raceway itself. It is usually expressed as a multiple of the cable's overall diameter and is checked during rough-in inspections.

The required internal volume of an outlet, device, or junction box based on the number and size of conductors, devices, fittings, and equipment grounds entering it. Each item is assigned a volume allowance and the total must not exceed the box's marked capacity.

A load expected to operate at maximum current for three hours or more, such as store lighting or a water heater. Branch circuits and overcurrent devices serving continuous loads must be sized larger than the load itself.

A load that operates at maximum current for less than three hours at a time, such as a typical receptacle outlet or an intermittent appliance. It is counted at its full calculated value without the extra sizing margin required for continuous loads.

The ratio of the maximum demand on a system to the total connected load. Applying it lets designers size services and feeders for realistic simultaneous use rather than the sum of every load at once.

The sum of the nameplate ratings of all equipment that could operate on a service or feeder at the same time. It is the starting point for a load calculation before demand factors and diversity are applied.

A documented method of totaling general lighting, receptacles, appliances, motors, heating, cooling, and other loads to determine the minimum service, feeder, and conductor sizes. Standard and optional methods exist, and the results must be shown on plans.

The conductors that carry power from the utility's point of delivery to the service equipment disconnect. Their size depends on the calculated load, and they are protected by the service overcurrent device rather than by a downstream breaker.

The set of conductive elements in direct contact with the earth, such as ground rods, metal water pipe, concrete-encased electrodes, and ground rings, that establishes a reference to earth. All available electrodes must be bonded together into one system.

The conductor that connects the grounding electrode system to the service equipment or source enclosure. Its size is based on the rating of the service or derived system rather than on the circuit conductors.

The conductor that provides a low-impedance path from the metal enclosures of equipment back to the source, allowing a fault to trip the overcurrent device. It normally carries no current except during a ground fault.

A conductor that ensures electrical continuity between metal parts that must be at the same potential, such as service raceways, water piping, and equipment enclosures. Bonding prevents dangerous voltage differences during faults.

A device that de-energizes a circuit within a set time when it senses a small current imbalance between the ungrounded and grounded conductors, indicating current is leaking to ground. It protects people from shock rather than equipment from overload.

A device that detects the characteristic current signature of a dangerous arcing fault in branch-circuit wiring and opens the circuit. It is required in many dwelling-unit circuits to reduce the risk of electrical fire.

The current value at which a fuse or circuit breaker is intended to open under specified conditions. The rating must protect the conductor while still carrying the calculated load, including the extra margin for continuous loads.

The maximum short-circuit current a supply system can deliver at a given point, determined by the utility transformer, service conductors, and circuit impedance. Equipment must be rated to withstand this current until a protective device clears the fault.

The highest fault current a circuit breaker or fuse can safely interrupt without damage or hazardous failure. It must equal or exceed the available fault current at the device's location.

An arrangement in which a downstream breaker with a lower interrupting rating is protected by an upstream current-limiting device, as verified by the manufacturer's listing. It may only be applied where the combination is tested and marked.

The current a motor draws at rated load and rated voltage, taken from tables rather than the motor nameplate for conductor and protection sizing. It is the basis for branch-circuit conductors, overload sizing, and feeder calculations.

A device, such as a thermal overload relay or heater element, that protects the motor from sustained overcurrent due to mechanical binding or loss of a phase. It is sized from the motor's nameplate current and does not protect the branch-circuit conductors.

A switch or device that isolates the motor and controller from all ungrounded supply conductors so maintenance can be performed safely. It must be within sight of the controller or capable of being locked open.

An area where flammable gases, vapors, or liquids are or may be present in quantities sufficient to produce an explosive or ignitable mixture. Equipment there must be listed for the specific class, division or zone, and group.

An area made hazardous by combustible dust, such as grain, coal, or metal dust, in quantities that could ignite. Wiring methods and equipment must be dust-ignition-proof or otherwise listed for the specific dust group.

A circuit designed so that any spark or thermal effect it produces cannot ignite a hazardous atmosphere under normal or specified fault conditions. It typically relies on energy-limiting barriers and is permitted in hazardous locations without explosion-proof enclosures.

A required safety procedure that de-energizes equipment, isolates all energy sources, applies personal locks and tags, and verifies the absence of voltage before work begins. It protects workers from unexpected energization or stored energy release.

A code term meaning acceptable to the authority having jurisdiction. It is not a synonym for listed; equipment can be approved for a specific installation even when listing is not required, and the inspector makes that judgment.

The organization, office, or individual responsible for enforcing the electrical code and approving equipment, materials, and installations. Inspectors interpret code requirements and may grant approvals or require corrections during plan review and field inspection.

Equipment, materials, or services included in a published list by an organization concerned with product evaluation that maintains periodic inspection of production. Listing by a recognized testing laboratory supports approval by the authority having jurisdiction.