HI Electrician key terms

The fixed relationship among voltage, current, and resistance in a circuit, expressed as E = I × R. Knowing any two values lets you calculate the third, making it the basis for most circuit troubleshooting and load calculations.

The relationship P = E × I, where power in watts equals voltage times current. In resistive circuits it can be combined with Ohm's law to yield P = I²R or P = E²/R for sizing conductors and overcurrent devices.

A circuit with only one current path, so the same current flows through every component while voltage divides across them and total resistance is the sum of individual resistances.

A circuit in which components connect across the same two points, so voltage is common to all branches while current divides among them and total resistance is always less than the smallest branch resistance.

The ratio of real power in watts to apparent power in volt-amperes in an alternating-current circuit. Low power factor increases current for a given load and affects conductor and service sizing for motor circuits.

The product of voltage and current in an AC circuit without regard to phase angle, measured in volt-amperes. It is the value used for sizing transformers, generators, and service equipment.

The loss of voltage along conductors caused by their resistance and reactance as current flows. Excessive drop causes dim lights and overheated motors, so feeders and branch circuits are checked against recommended percentages.

The current a motor draws at rated load and rated voltage, taken from code tables rather than the nameplate for conductor and overcurrent sizing purposes. It differs from nameplate current and drives most motor circuit calculations.

The ratio of the maximum demand on a system to the total connected load. Applying it allows service and feeder sizing based on realistic simultaneous use rather than the sum of every load.

The maximum current a conductor can carry continuously under stated conditions without exceeding its temperature rating. It depends on conductor size, insulation type, ambient temperature, and the number of current-carrying conductors bundled together.

The process of reducing a conductor's tabulated ampacity for high ambient temperature and for more than three current-carrying conductors in a raceway or cable, using code tables before applying overcurrent device ratings.

A device such as a circuit breaker or fuse that opens a circuit when current exceeds a set value, protecting conductors from overheating. Its rating must coordinate with conductor ampacity and equipment requirements.

A device that compares current leaving and returning on a circuit and trips when a small imbalance indicates current leaking to ground, protecting people from shock in bathrooms, kitchens, outdoors, and other specified locations.

A protective device that detects the signature of arcing in branch-circuit wiring and de-energizes the circuit, reducing the chance of fire from damaged or loose conductors. Required in many dwelling-unit branch circuits.

The method of totaling general lighting, receptacle, appliance, motor, and other loads with applicable demand factors to determine the minimum ampacity of service and feeder conductors and the rating of service equipment.

The sum of the ratings of all equipment and devices connected to a system, before any demand factors are applied. It is the starting point for feeder and service calculations.

The required clear space in front of electrical equipment, defined by voltage and condition, that must be kept free of obstructions so a worker can safely service energized parts.

The reserved zone above and in front of electrical equipment that must be kept clear of piping, ducts, and other foreign systems so equipment can be accessed and serviced safely.

The limit on how much of a conduit's cross-sectional area may be occupied by conductors, set by code tables for one, two, or more conductors. Exceeding it makes pulling difficult and traps heat.

The required minimum volume of an outlet, junction, or device box based on the number and size of conductors, devices, clamps, and grounding conductors it contains, preventing overcrowding and damaged insulation.

Forming raceways with hand or mechanical benders to produce accurate bends, offsets, and saddles while respecting minimum radii and limiting the number of bends between pull points.

A support system of rails and rungs that carries and supports cables, often in industrial and commercial work. Fill, support spacing, and bonding rules apply to keep cables from overheating or being damaged.

Protection that senses excessive current over time in a motor branch circuit and opens the circuit before the motor's windings are damaged, sized to allow normal starting current without tripping.

A device or assembly that starts, stops, reverses, or regulates a motor, including starters, contactors, and variable-frequency drives. It must be rated for the motor's voltage, current, and duty.

An electronic controller that varies the frequency and voltage supplied to an AC motor to control speed and torque, reducing energy use on variable-load equipment and introducing harmonic and grounding considerations.

A switch or device that isolates equipment from its supply so it can be safely serviced. It must be readily accessible, correctly rated, and marked, and its location relative to the equipment is regulated.

The state credential issued by the Hawaii Board of Electricians and Plumbers that authorizes a business to offer electrical contracting services, obtained through qualifying experience and examination and renewed on a set cycle.

The Hawaii license that permits an individual to perform electrical work unsupervised, generally earned through documented apprenticeship hours and passage of a trade examination administered under the state licensing board.

A licensed individual who oversees electrical work and, under Hawaii rules, may be required to qualify a contracting business by meeting experience and examination requirements and remaining actively involved in its operations.

The periodic training hours a Hawaii licensee must complete and document to renew a license, intended to keep practitioners current on code changes and safety practices.

The obligation to obtain the required county or state permit before starting regulated electrical work and to have the installation inspected, ensuring work complies with adopted codes before being energized or covered.

The conductor that connects the non-current-carrying metal parts of equipment to the system grounding point, providing a low-impedance path so fault current trips the overcurrent device.

The set of electrodes, such as ground rods, metal water pipe, or concrete-encased electrodes, bonded together and connected to the service to establish a reference to earth.

A conductor that intentionally connects metal parts to ensure electrical continuity and equal potential, such as across water meters, gas piping, or structural steel, preventing dangerous voltage differences during faults.

The safety procedure of de-energizing equipment, applying a lock and tag, and verifying absence of voltage before working on it, protecting the worker from unexpected energization or stored energy.

Clothing and gear such as insulated gloves, arc-rated clothing, and face shields selected for the incident-energy and shock hazards of the task, forming the last line of defense against electrical injury.