ELECTRICAL GLOSSARY

ampacity: maximum amount of current a wire can carry safely without overheating

amperage: strength of an electrical current, measured in amperes

Ampere: The unit by which the flow of current through a conductor is measured.

Arc: A discharge of electricity through a gas, such as air.

arc-blast: explosive release of molten material from equipment caused by high-amperage arcs

arcing: luminous electrical discharge (bright, electrical sparking) through the air that occurs when high voltages exist across a gap between conductors

Attachment Cap: See Plug.

AWG: American Wire Gauge—measure of wire size

bonding: joining electrical parts to assure a conductive path bonding

Circuit: The path along which electric current flows from start to finish is called a circuit. The circuit includes the generator or battery which starts the current, the wires, and any electrical device that the current operates. If any part of the circuit is removed, the current cannot flow. The circuit is then broken or open. Because electric current seeks to complete its circuit, it will travel along any path that is presented (path of least resistance), which is why humans are at risk of electrocution when they handle damaged tools or cords, or contact un-insulated wires. In effect, they become part of the circuit.

Circuit breaker: A protective device which automatically opens, or trips, a circuit, without damage to itself, when the current exceeds a predetermined level.

Conductor: A substance or body that allows a current of electricity to pass continuously along it. Metals, such as copper or aluminum, are good conductors. In a circuit, current-carrying wires are termed "conductors", as in a flexible cord.

CPR: cardiopulmonary resuscitation—emergency procedure that involves giving artificial breathing and heart massage to someone who is not breathing or does not have a pulse (requires special training)

Current: The flow of electrons through a conductor, measured in amperes (amps). If the current flows back and forth through a conductor, it is called alternating current (AC). If the current flows in one direction only, as in a car battery, it is called direct current (DC). AC is most widely used because it is possible to increase ("step up") or decrease ("step down") the current through a transformer. For example, when current from an overhead power line is run through a pole-mounted transformer, it can be stepped down to normal household current. Also, alternating current can travel enormous distances with little loss of voltage, or power.

Cycle: When alternating current flows back and forth through a conductor, it is said to cycle. In each cycle, the electrons flow first in one direction, then the other. In the United States, the normal rate for power transmission is 60 cycles per second, or 60 Hertz (Hz).

De-energize: To free from any electric connection and/or electric charge.

double-insulated: equipment with two insulation barriers and no exposed metal parts

Electricity: The flow of an atom's electrons through a conductor.

Electrode: A conductor used to establish electrical contact with a nonmetallic part of a circuit.

Energize: To direct electric current through a conductor. Power lines and wires can be intentionally energized (or de-energized) to carry current to an electrical device. But conductive surfaces which are unintentionally energized, like the metal case of a tool, the metal housing of a circuit box, or a metal object such as an aluminum ladder, present a danger of electrocution.

energized (live, “hot”): similar terms meaning that a voltage is present that can cause a current, so there is a possibility of getting shocked Fault: An insulation failure that exposes electrified conductors, causing current to leak and possibly resulting in electric shock.

fault current: any current that is not in its intended path

fixed wiring: permanent wiring installed in homes and other buildings

flexible wiring: cables with insulated and stranded wire that bends easily

Fuse: A protective device which allows a piece of metal to become part of a circuit. The metal melts under heat created by excessive current, thereby interrupting the circuit and preventing the flow of electricity from exceeding the circuit's current-carrying capacity.

GFCI: (Ground-fault circuit interrupter): A device that detects an insulation failure by comparing the amount of current flowing to electrical equipment with the amount of current returning from the equipment. Whenever the difference is greater than 5 milliamps, the GFCI trips and thereby interrupts the flow of electricity.

Ground: A conducting connection, intentional or unintentional, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth.

Ground-fault: A fault, or insulation failure, in the wire used to create a path to ground.

Grounding: To prevent the buildup of hazardous voltages in a circuit by creating a low-resistance path to earth or some other ground plane.

ground potential: voltage a grounded part should have; 0 volts relative to ground

Guarding: Placement of live parts of electrical equipment where they cannot accidentally be contacted, such as in a vault, behind a shield, or on a raised platform, to which only qualified persons have access.

Impedance: Opposition to the flow of alternating (AC) electric current. See Resistance.

Insulation: Non-conductive materials used to cover or surround a conductor, permitting it to be handled without danger of electric shock.

Insulator: Any material, such as glass or rubber, that prevents the flow of electric current.

jumper: conductor used to connect parts to be bonded

Kilowatt: One thousand watts.

leakage current: current that does not return through the intended path, but instead "leaks" to ground

Lockout: To lock a switch in the "off" position by means of a padlock, or to lock electrified equipment behind a locked door, to which only qualified persons have the key.

Low-Impedance: Low resistance to A/C current.

Milliampere: A unit of measurement equaling one thousandth (1/1000) of an ampere.

NEC: National Electrical Code—comprehensive listing of practices to protect workers and equipment from electrical hazards such as fire and electrocution

neutral: at ground potential (0 volts) because of a connection to ground

NFPA 70E: Standard for Electrical Safety in the Workplace. This standard addresses those electrical safety requirements for employee workplaces that are necessary for the practical safeguarding of employees. It covers the installation of electrical conductors, electrical equipment, signaling and communications conductors and equipment, and raceways, excluding generating plants, substations, and control centers.

Ohm: The unit by which resistance to electrical current is measured. From Ohm's Law (Current=Voltage/Resistance, or in other words, Current=Voltage/Ohms), a mathematical expression of the relationship between these three elements.

Overcurrent: Any current in excess of the rated capacity of equipment or of a conductor.

overload: too much current in a circuit

Phase: In AC power systems, load current is drawn from a voltage source which typically takes the form of a sine wave. Ideally, the current drawn by the loads in the system is also a sine wave. With a simple, resistive load such as a light bulb, the current sine wave is always aligned with the voltage sine wave. This is called single-phase. A single-phase power system normally uses three wires, called hot, neutral, and ground, and the voltage is typically 120/240. Most home and office outlets operate in this manner. With some loads, such as motors, and in high voltage systems, the current sine wave is purposely delayed and lags behind the voltage sine wave. The amount of this lag is expressed in degrees and is called a phase difference. A common example is three-phase power, where the system has three "hot" wires, each 120 degrees out of phase with each other.

Plug: A device to which the conductors of a cord are attached, which is used to connect to the conductors permanently attached to a receptacle.

Polarity: The relationship between poles of positive and negative charge, particularly with regard to wiring of conductors where the ungrounded (hot) conductor and grounded (neutral) conductor form a circuit.

power: amount of energy used each second, measured in watts

PPE: personal protective equipment (eye protection, hard hat, special clothing, etc.)

qualified person: someone who has received mandated training on the hazards and on the construction and operation of equipment involved in a task. One familiar with the construction and operation of the equipment and the hazards involved.

Rating: The stated operating limit of a piece of equipment, expressed in a unit of measure such as volts or watts.

Raceway: A channel designed expressly for holding wires, cables, or busbars, including conduit, tubing, wireways, busways, gutters, or moldings.

Receptacle: A device, such as a jack or an outlet, to which conductors are attached, and where a plug makes contact with a source of electric current.

Resistance: Anything that impedes the flow of electricity, particularly in direct (DC) current.  Resistance is measured in ohms.

risk: chance that injury or death will occur

shocking current: electrical current that passes through a part of the body

short: low-resistance path between a live wire and the ground, or between wires at different voltages (called a fault if the current is unintended)

Tag: To identify electric equipment by class, group, and the temperature range for which it is approved.

tag-out: applying a tag that alerts workers that circuits and equipment have been locked out

trip: automatic opening (turning off) of a circuit by a GFCI or circuit breaker

Volt: The unit by which electrical force or pressure is measured.

Voltage: The fundamental force or pressure that causes electricity to flow through a conductor. Measured in volts.

Watt: The unit by which electric energy, or the ability of electricity to do work, is measured. A thousand watts, or one kilowatt, equals 1.34 horsepower.

wire gauge: wire size or diameter (technically, the cross-sectional area)