Plain definitions of 35 terms we use on the job in San Bernardino.
Term Index
Open any term below for a dedicated definition page.
An Arc-Fault Circuit Interrupter is a protective device that monitors electrical current for patterns linked to unintended arcing. When the device detects those patterns, it opens the circuit to stop power flow. AFCI protection helps address faults that ordinary overcurrent devices may not identify quickly because the current may remain below their trip level.
Also called: AFCI
Ballast is a device in certain fluorescent and high-intensity discharge light fixtures that controls electrical current through the lamp. The ballast helps the lamp start, limits current during operation, and supports steady light output. Modern LED fixtures often use a separate driver instead of a traditional ballast.
A branch circuit is the portion of an electrical system that carries power from a panelboard overcurrent device to connected outlets, lighting, or equipment. Conductors, the circuit breaker, and connected loads work together as one path. The circuit may serve general-use devices or equipment that needs its own dedicated supply.
Busbar is a conductive metal bar or strip inside an electrical panel that distributes power to connected circuits. It provides a common connection point for circuit breakers and carries current across the panel. Insulating supports, barriers, and panel design keep the busbar separated from grounded or neutral components where required.
A circuit directory is a written map of an electrical panel that identifies which rooms, outlets, lights, or appliances each circuit supplies. The directory usually appears on the panel door or cover. Accurate labels help electricians isolate power, trace faults, plan panel changes, and restore the correct circuit after maintenance.
Also called: Panel Schedule
Conduit is a protective pathway for electrical conductors. It may be made from metal or nonmetallic material and can run through walls, ceilings, floors, or exposed areas. Conduit shields wires from physical damage, organizes cable routes, and allows conductors to be replaced or modified without opening every finished surface.
A continuity test is an electrical check that determines whether a complete conductive path exists between two points. A meter applies a small test current and evaluates the resulting resistance. A low-resistance path generally indicates continuity, while a very high reading or open indication points to a break, loose connection, or disconnected component.
Current is the movement of electric charge through a conductor, such as a wire, circuit path, or device. Electrical current describes how much charge flows and in which direction. Technicians measure current in amperes, often called amps, to assess circuit loading, locate faults, and confirm that equipment operates within its intended electrical conditions.
Also called: Amperage
A dimmer switch is a wall control that adjusts the brightness of a compatible light by regulating electrical power to the fixture. Unlike a standard on-off switch, a dimmer provides a range of light levels. Compatibility depends on the dimmer design, lamp type, fixture, and wiring arrangement.
Electrical Load is the amount of electrical power a device, circuit, or building draws while operating. The load depends on the equipment connected to the system and how that equipment runs. Electricians assess load before assigning circuits, selecting conductors, and checking whether existing electrical equipment can support added demand safely.
Also called: Load Demand
A Ground Fault is an unintended electrical connection between an energized conductor and grounded metal, equipment, or earth. This connection allows current to follow an abnormal path. A ground fault may create shock and fire hazards, so protective devices such as ground-fault circuit interrupters can disconnect power when they detect the condition.
Grounding Electrode is a conductive object, such as a ground rod or metal water pipe, that connects an electrical system to the earth. The connection helps direct electrical energy from faults, lightning, or surges into the soil. A grounding electrode is different from the wire that connects equipment to the electrode.
A ground rod is a conductive metal electrode driven into the earth to connect an electrical grounding system with the soil. The rod provides a path for fault current and helps stabilize electrical potential during abnormal conditions. It connects to grounding conductors that bond equipment, panels, and other parts of the electrical system.
Also called: Grounding Rod
A hot wire is an energized conductor that carries electrical potential from a power source toward a load, such as a light, receptacle, or appliance. The wire typically connects to the ungrounded side of a circuit. Its voltage can be present even when the connected device is switched off, depending on the circuit design.
Also called: Live Wire
Junction Box is an enclosed electrical box that houses wire connections, splices, or branch-circuit transitions. The enclosure protects the connections from physical damage and keeps wiring organized. Conductors enter through approved openings, connect with suitable devices, and remain accessible for inspection, testing, or future repair without being buried inside a wall or ceiling.
Also called: Electrical Junction Box
An LED Driver is an electronic power-conversion device that supplies LEDs with the voltage or regulated current required to produce steady light. The driver adapts incoming electrical power to the requirements of an LED fixture. Depending on its design, the driver may also support dimming, thermal protection, or communication with lighting controls.
Also called: LED Power Supply
A light socket is the electrical component that holds a lamp and connects it to the fixture wiring. The socket transfers current through contact points to the lamp base. Different socket designs match different lamp bases and fixture types. A socket may be built into a ceiling fixture, wall fixture, table lamp, or outdoor light.
Also called: Lamp Socket
Line Voltage is the electrical pressure supplied by a power system to operate equipment, lighting, and receptacles. The term usually describes voltage present on a building circuit before a device changes it for a specific function. Electricians assess line voltage at conductors, terminals, or outlets to confirm that power reaches the intended equipment.
Also called: Mains Voltage
Motion Sensor is a device that detects movement within a defined area and signals a light or control system to respond. Common sensors detect changes in infrared energy, sound waves, or reflected microwaves. In security lighting, the sensor turns a connected fixture on when movement meets its detection settings, then allows the light to turn off later.
Also called: Occupancy Sensor
A Neutral Wire is a current-carrying conductor that returns electricity from a load to the electrical panel and completes a circuit. It is commonly connected to the neutral bus in the panel and often has white or gray insulation. A neutral wire is distinct from a hot wire and a grounding conductor.
Also called: Neutral Conductor
An ohm is the unit used to measure electrical resistance, which describes how strongly a material or circuit opposes current flow. Resistance affects how much current a given voltage can produce. Electricians use ohms when testing wires, components, and circuits for unwanted resistance, open paths, or shorted conditions.
An overloaded circuit is a branch circuit carrying more electrical current than its wiring or protective device is designed to handle. The excess demand often comes from several appliances, tools, or fixtures operating on the same circuit. The added load can trip the circuit breaker and may cause abnormal heat at wiring connections.
Photocell is a light-sensitive electrical control that switches outdoor lighting on when surrounding light fades and off when daylight returns. The device responds to ambient brightness through a sensor, so landscape lights follow natural light conditions without manual switching. Photocells commonly control path lights, garden lights, wall fixtures, and other exterior lighting.
Also called: Photoelectric Sensor
Power outage is a temporary loss of electrical service to a home, building, circuit, or wider area. The interruption may result from utility equipment, damaged wiring, a tripped breaker, severe weather, or a fault in private electrical equipment. Restoring service requires identifying the affected part of the electrical system and correcting the cause.
Also called: Blackout
A Short Circuit is an unintended low-resistance path between electrical conductors that allows excessive current to flow. The path may form between hot and neutral wires, hot and ground, or damaged components. This fault can trip a circuit breaker, blow a fuse, damage equipment, create heat, and interrupt power to part of a property.
A surge protector is a device that limits brief increases in electrical voltage before those changes reach connected equipment. It directs excess energy away from sensitive electronics through protective components and a grounding path. Surge protectors appear in plug-in power strips, receptacles, and service equipment, with protection suited to the installation.
Also called: Surge Suppressor
A tamper-resistant outlet is an electrical receptacle with internal shutters that block access to its energized contacts unless a matching plug enters both slots at once. The shutters help prevent accidental insertion of objects into the outlet openings. Tamper-resistant outlets serve as a protective receptacle choice in homes, workplaces, and other occupied spaces.
Also called: TR Outlet
Thermal Imaging is a noncontact inspection method that uses an infrared camera to display differences in surface temperature. Electrical professionals review these patterns to locate unusual heating at panels, breakers, terminals, conductors, and connected equipment. The method supports visual inspection and electrical testing, but it does not show hidden damage directly.
Also called: Infrared Inspection
A Three-Way Switch is a wall switch arrangement that lets you control one light or lighting group from two separate locations. The arrangement uses two compatible switches connected by traveler wires, allowing either switch to change the circuit path. It is common in hallways, stairways, bedrooms, and rooms with multiple entrances.
A transfer switch is an electrical device that moves selected circuits between normal utility power and a standby generator. The switch prevents both power sources from feeding the same circuit at once. Manual models require a person to change sources, while automatic models sense an outage and control the changeover.
Also called: Generator Transfer Switch
Voltage Drop is the reduction in electrical pressure that occurs as current travels through a conductor, connection, or device. The reduction increases with circuit length, electrical load, and resistance. Excessive voltage drop can make lights dim, motors run poorly, or equipment fail to receive the voltage required for proper operation.
A voltage tester is a handheld electrical testing tool that detects whether voltage is present in a wire, terminal, outlet, or other electrical point. Depending on its design, the tester may sense voltage without contact or use test leads to check electrical potential directly. It helps identify energized circuits during troubleshooting.
Also called: Non-Contact Voltage Tester
Wire Gauge is a standardized way to describe a conductor’s thickness. The gauge identifies the wire’s cross-sectional size, which affects how much electrical current the conductor can carry and how much resistance it presents. A smaller gauge number generally indicates a thicker conductor, while a larger gauge number indicates a thinner conductor.
Also called: AWG
Wire Nut is a twist-on connector that joins and insulates exposed electrical conductors inside an approved electrical box or enclosure. The connector uses an internal spring or threaded insert to grip the wires when tightened. Wire nuts come in different sizes and types, so the connector must match the conductors and connection.
Also called: Wire Connector
A wire stripper is a hand tool that removes insulation from an electrical conductor without cutting through the metal core. Its sized cutting notches match common wire gauges, while some models also crimp terminals or cut wire. Electricians use the tool during wiring repair to prepare clean conductor ends for connections.
