Electrical Engineering Glossary

The reduction in voltage along a conductor due to its electrical resistance. Occurs as current flows through wires and is proportional to wire length and current magnitude.

A standardized wire gauge system used primarily in North America. Lower AWG numbers indicate thicker wires with lower resistance and higher current capacity.

The opposition to current flow in an electrical conductor, measured in ohms. Depends on material, length, cross-sectional area, and temperature.

An AC power distribution method using two wires (hot and neutral). Common in residential applications and smaller commercial loads.

An AC power distribution method using three conductors carrying currents 120° out of phase. More efficient for large loads and motors.

The rotational force produced by a motor shaft, calculated as T = P/ω where P is power and ω is angular velocity. Measured in N·m or lb·ft. Determines acceleration capability and load driving ability.

The ratio of mechanical output power to electrical input power, expressed as a percentage. Losses include copper (I²R), iron (core), mechanical (friction), and stray load losses.

The ratio of real power (kW) to apparent power (kVA) in an AC motor. Indicates how effectively the motor uses electrical power. Low power factor increases current draw and electrical losses.

The fundamental relationship between voltage (V), current (I), and resistance (R) in an electrical circuit: V = I × R. This law states that the current through a conductor is directly proportional to the voltage and inversely proportional to the resistance.

The opposition to current flow in an electrical circuit, measured in ohms (Ω). Resistance depends on material resistivity (ρ), conductor length (L), and cross-sectional area (A): R = ρL/A.

The flow of electric charge through a conductor, measured in amperes (A). One ampere equals one coulomb of charge passing a point per second. Current flows from positive to negative (conventional) or negative to positive (electron flow).

The rate at which electrical energy is converted to heat in a circuit, measured in watts (W). Calculated as P = V × I, P = I²R, or P = V²/R. Power dissipation determines thermal management requirements.

The maximum current a conductor can carry continuously without exceeding its temperature rating. Ampacity depends on conductor size, insulation type, installation method, and ambient conditions. Defined in NEC Table 310.16.

A load where the maximum current is expected to continue for 3 hours or more. Per NEC 210.20, conductors for continuous loads must be sized at 125% of the load current to account for sustained heat buildup.

The maximum continuous operating temperature of a conductor's insulation, typically 60°C, 75°C, or 90°C. Higher ratings allow more current, but terminations (breakers, outlets) often limit usable ampacity to 75°C values.

The number of conductors installed in a raceway, which affects ampacity derating. More conductors mean less heat dissipation per wire. NEC Table 310.15(C)(1) specifies adjustment factors based on conductor count.