Electrical Terms

Ambient Temperature: It is the temperature of the air, water, or surrounding earth. Conductor ampacity is corrected for changes in ambient temperature including temperatures below 86°F. The cooling effect can increase the current carrying capacity of the conductor.

Ammeter: An electric meter connected in series to the circuit used to measure current, calibrated in amperes.

Ampacity: The amount of electric current a conductor can carry without exceeding its specified temperature, in amperes

Ampere: The base unit of electric current in the International System of Units that is equal to a constant current which when maintained in two straight parallel conductors of infinite length and negligible circular sections one meter apart in a vacuum produces between the conductors a force equal to 2 × 10−7 Newton per meter of length.

Ampere–hour (Amp-Hours or Ah): A unit quantity of electricity equal to the quantity carried past any point of a circuit in one hour by a steady current of one ampere.

Amplifier: An electrical circuit that produces an output that is a replica of the input. The output may be scaled or have increased drive, or it may provide isolation such that changes in output conditions do not affect the input or other outputs. It may perform transformations like filtering or logarithmic drive.

Arc-over Voltage: The minimum voltage required to cause an arc between electrodes separated by a gas or liquid insulation.

Armored Cable: A cable provided with a wrapping of metal, usually steel wires or tapes, primarily for the purpose of mechanical protection.

Attenuation: (l) The ratio of the input to output power levels in a network (transmission line) when it is excited by a matched source and terminated in a matched load. (2) Power loss in an electrical system.

Bare Conductor: A conductor not covered with insulating material.

Base Load: That portion of electricity demand on a utility system that remains at a nearly steady level.

Base Rates:That portion of a utility's prices covering investment in power plants, substations, wires, poles, equipment and daily operating costs.

Clamp meter: It contains a current transformer and is used to measure current in one phase of a cable. It is also called a tongue tester.

Electric battery: A battery (or voltaic pile) is a device for making electricity by chemical means. In the 1790s, Alessandro Volta (1745-1827) discovered that if pieces of different metals were piled on top of each other separated by cardboard soaked in an acid, an electric current was produced. Despite all the developments since, the principle of the battery remains the same.

Electricity: These days, electricity is thought of in terms of the flow of electrons (tiny charged particles) passing along a wire. It is the manifestation of a form of energy. From the 18th century to the middle of the 19th century, though, electricity was thought of as an imponderable (weightless) material fluid (or fluids) flowing through a wire, the way water flows through a pipe. Michael Faraday was the first to argue that electricity was a force. However, he opposed the atomic conception of matter and was therefore unable to make the leap to an electron theory.

Electric motor: A machine that converts electrical energy into mechanical energy. An early form was invented by Michael Faraday in 1821. He found that a wire carrying an electric current rotated round a magnet. Thus he demonstrated that it was possible to obtain motion from the combination of electricity and magnetism. This encouraged the development of the modern electric motor which uses the interaction of magnetic fields, produced electrically, to cause motion.

Electro-magnetic rotations: The principle behind the electric motor. In 1821, Michael Faraday discovered that a vertically mounted wire carrying an electric current would rotate continuously round a magnet protruding from a bowl of mercury. This phenomenon, which Faraday called electro-magnetic rotations, showed that it was possible to produce continuous motion from the interaction of electricity and magnetism.

Electro-magnetism: Electro-magnetism describes the relationship between electricity and magnetic force. Certain metals can be made magnetic by passing an electric current through a coil wound around a piece of them. A report of the discovery of this effect was published in 1820 by Hans Christian Oersted (1777-1851).

Bayonet Coupling: A quick coupling device for plug and receptacle connectors, accomplished by rotation of a cam operating device designed to bring the connector halves together.

Beryllium Copper (Be Cu): A relatively expensive contact material with properties superior to brass and phosphor bronze. It is recommended for contact applications requiring repeated extraction and reinsertion because of its resistance to fatigue at high operating temperatures.
Bonding Jumper: A bare or insulated conductor used to ensure the required electrical conductivity between metal parts required to be electrically connected. Frequently used from a bonding bushing to the service equipment enclosure to provide a path around concentric knockouts in an enclosure wall: also used to bond one raceway to another.

Breakdown Voltage: The voltage at which an insulator or dielectric ruptures, or at which ionization and conduction take place in a gas or vapor.
British Thermal Unit (BtU): Standard unit of heat measurement, equal to raising one pound of water one degree Fahrenheit at sea level pressure.

Cable: Either a stranded conductor with or without insulation and other coverings (single-conductor cable), or a combination of conductors insulated from one another (multiple-conductor cable).

Cable Assembly: A cable with plugs or connectors on each end.

Capacitance: That property of a system of conductors and dielectrics that permits the storage of electricity when potential difference exists between the conductors. Its value is expressed as the ratio of quantity of electricity to a potential difference. A capacitance value is always positive.

Capacity: The load for which an electric generating unit, other electrical equipment or power line is rated.

Certificate of Convenience and Necessity: a term used by public service commissions in granting authority to a company to render utility service, usually specifying the area and other conditions of service.

Closed Entry Contact: A female contact designed to prevent the entry of a pin or probing device having a cross-sectional dimension (diameter) greater than the mating pin.

Coaxial Cable: A high-band width cable consisting of two concentric cylindrical conductors with a common axis that is used for high-speed data communication and video signals.

Cogeneration: Joint production of electricity and useful heat/steam from a common source.

Component Lead: The solid or stranded wire or formed conductor that extends from a component and serves as a readily formable mechanical or electrical connection or both.

Concentricity: In a wire or cable, the measurement of the location of the center of the conductor with respect to the geometric center of the surrounding insulation.

Conductance: The reciprocal of resistance. It is the ratio of current passing through a material to the potential difference at its ends.

Conductivity: The ability of a material to conduct electric current. It is expressed in terms of the current per unit of applied voltage. It is the reciprocal of resistivity.

Conductor: Any material (such as a power line) that allows its electrons to be easily transferred.

Connector: A device providing electrical connection/disconnections. It consists of a mating plug and receptacle. Various types of connectors include DIP, card edge, two-piece, hermaphroditic and wire-wrapping configurations. Multiple contact connectors join two or more conductors with others in one mechanical assembly.

Contact, Female: A contact located in an insert or body in such a manner that the mating contact is inserted into the unit. It is similar in function to a socket contact.

Contact, Male: A contact located in an insert or body in such a manner that the mating portion extends into the female contact. It is similar in function to a pin contact.

Contact Resistance: Maximum permitted electrical resistance of pin and socket contacts when assembled in a connector under typical service use.

Contact Size: Defines the largest size wire that can be used with the specific contact. By specification dimensioning, it also defines the diameter of the engagement end of the pin.

Continuous Load: A load where the maximum current is expected to continue for three hours or more. Rating of the branch circuit protection device shall not be less tan 125% of the continuous load.

Demand Charge: A separate charge based upon the demand for electric service by a commercial or industrial customer, based on the investment in facilities necessary to serve them.

Demand Factor: For an electrical system or feeder circuit, this is a ratio of the amount of connected load (in kva or amperes) that will be operating at the same time to the total amount of connected load on the circuit. An 80% demand factor, for instance, indicates that only 80% of the connected load on a circuit will ever be operating at the same time. Conductor capacity can be based on that amount of load.

Diallyl Phthalate (DAP): A thermosetting plastic that offers outstanding dimensional stability and resistance to most chemicals and chemical compounds. It is used in the production of connector housings.

Dielectric: (l) Any insulating medium that intervenes between two conductors. (2) A material that, having the property required to establish an electric field, is recoverable in whole or in part as electric energy.

Dielectric Constant: That property of a dielectric that determines the electrostatic energy stored per unit volume for a unit potential gradient. Permittivity is the preferred term.

Dielectric Strength: The maximum voltage that a dielectric material can withstand, under specified conditions, without rupturing. It is usually expressed as volts/unit thickness. Also called Disruptive Gradient or Electric Strength.

Dielectric Withstanding Voltage: Maximum potential gradient that a dielectric material can withstand without failure.

Distribution Lines: Power lines, like those in neighborhoods, used to carry moderate voltage electricity which is "stepped down" to household levels by transformers on power poles.

Dustproof: Constructed or protected so that dust will not interfere with its successful operation.

Duty, continuous: A service requirement that demands operation at a substantially constant load for an indefinitely long time.

Duty, intermittent: A service requirement that demands operation for alternate intervals of load and no load, load and rest, or load, no load, and rest.

Duty, periodic: A type of intermittent duty in which the load conditions regularly reoccur.

Duty, short time: A requirement of service that demands operations at a substantially constant load for a short and definitely specified time.

Duty, varying: A requirement of service that demands operation at loads, and for intervals of time, both of which may be subject to wide variation.

Electricity: The flow of electrons through a conductor.

Electrostatic Precipitators: Pollution control devices attached to fossil fuel generating plants which prevent the vast majority of fly ash from being released into the air.

Eminent Domain: The authority to acquire land from a private owner for the benefit of public use.

Feeder: Power lines that travel out from substations to "feed" smaller distribution lines in a certain geographic area are called feeders.

Fly ash: Small particles of airborne ash produced by burning fossil fuels.

Franchise fee: A local tax imposed on utilities for the privilege of providing a service within city limits.

Foot-candle (fc): One foot-candle ≈ 10.764 lux. The foot-candle (or lumen per square foot) is a non-SI unit of illuminance. It is obsolete but it is still in fairly common use in the United States, particularly in construction-related engineering and in building codes. Because lux and foot-candles are different units of the same quantity, it is perfectly valid to convert foot-candles to lux and vice versa.

Fuel adjustment Clause: An annual adjustment in rates based on changes in the price of fuel used to generate electricity.

Galvanometer: A device for showing the presence and measuring the quantity of electricity. When an electrical current is passed through the coil of a galvanometer, a magnetic needle near the coil is deflected. This can be calibrated to provide a measure of the quantity of electricity. The galvanometer was invented following Hans Christian Oersted's discovery of electro-magnetism in 1820, and was named after Alessandro Volta's great electrical rival, Luigi Galvani.

Generator: The electric generator was invented by Michael Faraday in 1831 in the course of his work exploring electro-magnetic induction. It's a device with a magnet, or something performing the function of a magnet, that moves in the vicinity of a coil of wire to generate an electric current in the wire. Virtually all electric power is produced using this principle, no matter whether the prime source of energy is coal, oil, gas, nuclear, hydro, or wind, etc.

Ground: A large conducting body (as the earth) used as a common return for an electric circuit and as an arbitrary zero of potential.

Grounded, effectively: Intentionally connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connect equipment or to persons.

Grounded Conductor: A system or circuit conductor that is intentionally grounded, usually gray or white in color.

Grounding Conductor: A conductor used to connect metal equipment enclosures and/or the system grounded conductor to a grounding electrode, such as the ground wire run to the water pipe at a service; also may be a bare or insulated conductor used to ground motor frames, panel boxes, and other metal equipment enclosures used throughout electrical systems. In most conduit systems, the conduit is used as the ground conductor.

Grounding Electrode: The conductor used to connect the grounding electrode to the equipment grounding conductor, to the grounded conductor, or to both, of the circuit at the service equipment or at the source of a separately derived system.

Ground Fault Circuit Interrupter: A device intended for the protection of personal that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than required to operate the over current protection device of the supply circuit.

Ground Fault Protection of Equipment: A system intended to provide protection of equipment from damaging line to ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operations of a supply circuit over current device.

High voltage: Voltage greater than 100,000 volts.

Insulation: A material that offers high electric resistance making it suitable for covering components, terminals and wires to prevent the possible future contact of adjacent conductors resulting in a short circuit.

Interrupter Rating: The highest current at rated voltage that a device is intended to interrupt under standard test conditions.

Jacket: Outermost layer of insulating material of a cable or wire.

Kilowatt (kW):1,000 watts.

Kilowatt-Hour (kWh): A unit of electricity consumption. A kilowatt-hour equals the amount of electricity needed to burn ten, 100-watt light bulbs for one hour.

Kilovolt (kV): 1,000 volts.

Light Emitting Diode (LED): A semiconductor diode that emits light when a voltage is applied to it and that is used especially in electronic devices (as for an indicator light).

Load: The total customer demand for electric service at any given time.

lumen (lm): The lumen (symbolized lm) is the International Unit of luminous flux. A unit of luminous flux is equal to the light emitted in a unit solid angle by a uniform point source of one candela intensity.

lux (lx): Lux is the amount of light you actually see. One lux is equal to one lumen per square meter. It is the amount of light cast on a surface. This is the most practical measurement of light.

Megawatt (MW): One million watts or 1,000 kilowatts.

Mega ohm: A unit of electrical resistance equal to one million ohms.

Mega ohmmeter: An instrument for measuring extremely high resistance.

Megger: A test instrument for measuring the insulation resistance of conductors and other electrical equipment; specifically, a mega ohm (million ohms) meter; this is a registered trade mark of the James Biddle Co.

Natural Monopoly: When the cost of utility service, such as gas, water or electric service, is minimized to customers if a single enterprise is the only seller in the market.

Non inductive Circuit: A circuit in which the magnetic effect of the current flowing has been reduced by one several methods to a minimum or to zero.

Nonlinear Load: A load where the wave shape of the steady state current does not follow the wave shape of the applied voltage.

Off-System Sales: Sales by a utility to a customer (usually another utility) outside of its authorized market.

Ohm: The derived SI unit for electrical resistance or impedance; one ohm equals one volt per ampere.

Ohm's law: Ohm's law relates electro-motive potential difference (V) to current (I) and resistance (R) using the formula V=IR. Georg Simon Ohm (1789-1854) published his law in 1827.

Ohmmeter: an instrument for measuring resistance in ohms. Take a look at this diagram to see how an ohmmeter is used to check a small control transformer. The ohmmeter's pointer deflection is controlled by the amount of battery current passing through the moving coil. Before measuring the resistance of an unknown resistor or electrical circuit, the ohmmeter must first be calibrated. If the value of resistance to be measured can be estimated within reasonable limits, a range selected that will give approximately half-scale deflection when the resistance is inserted between the probes. If the resistance is unknown, the selector switch is set on the highest scale. Whatever range is selected, the meter must be calibrated to read zero before the unknown resistance is measured.

"O" RING: A doughnut-shaped ring of rubber used as a seal around the periphery of the mating insulator interface of cylindrical connectors.

Over current: Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit or ground fault.

Overload: Load greater than the load for which the system or mechanism was intended. A fault, such as a short circuit or ground fault, is not an overload.

Panel board: A single panel or group of panel units designed for assembly in the form of a single panel includes buses and may come with or without switches and/or automatic over current protective devices for the control of light, heat, or power circuits of individual as well as aggregate capacity. It is designed to be placed in a cabinet or cutout box that is in or against a wall or partition and is accessible only from the front.

Peak Demand: A one hour period in a year representing the highest point of customer consumption of electricity.

Plenum: Chamber or space forming a part of an air conditioning system.

Power Factor: It is the cosine angle between voltage and current.

Power Pool: A regional organization of electric companies interconnected for the sharing of reserve generating capacity.

Peak Power: the maximum amount of power in watts (W) the generating equipment will produce.

Public Utility: A business enterprise rendering a service considered essential to the public and, as such, subject to regulation.

Rated Power: the maximum amount of wattage (W) the equipment is rated for
Scrubbers: Equipment designed to reduce sulfur emissions from coal-fired generating plants.

Separately Derived System: A premises wiring system whose power is derived from a battery, a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including solidly connected grounded circuit conductor, to supply conductors originating in another system.

Service Area: The territory in which a utility has the right to supply service.

Service Conductors: The set of wires, often bundled, that takes electricity from the transformer on the pole directly to the house or business. Referred to as service cable when installed underground. Also known as Service Wire.

Service Drop: Run of cables from the power company's aerial power lines to the point of connection to a customer's premises.

Service Entrance Conductors(Overhead): The service conductors between the terminals of the service equipment and a point usually outside the building, clear of building walls, where joined by tap or splice to the service drop.

Service Entrance Conductors (Underground): The service conductors between the terminals of the service equipment and the point of connection to the service lateral.

Service Equipment: The necessary equipment, usually consisting of a circuit breaker or switch and fuses and their accessories, located near the point entrance of supply conductors to a building and intended to constitute the main control and cutoff means for the supply to the building.

Service Lateral: The underground service conductors between the street main, including any risers at a pole or other structure or from transformers, and the first point of connection to the service-entrance conductors in a terminal box, meter, or other enclosure with adequate space, inside or outside the building wall. Where there is no terminal box, meter, or other enclosure with adequate space, the point of connection is the entrance point of the service conductors into the building.

Service Point: The point of connection between the facilities of the serving utility and the premises wiring.

Shield: Device surrounding that portion of a connector that is used for attaching wires or cables to shield against electromagnetic interference, and/or protect connector wires or cable from mechanical damage.

Substation: A facility where the voltage of electricity is reduced prior to distribution to customers.

Switchboard: A large single panel, frame, or assembly of panels having switches, over current, and other protective devices, buses, and usually instruments mounted on the face or back or both. Switchboards are generally accessible from the rear and from the front and are not intended to be installed in cabinets.

Switch, general use: A switch intended for use in general distribution and branch circuits. It is rated in amperes and is capable of interrupting its rated voltage.

Switch, general-use snap: A type of general-use switch so constructed that it can be installed in flush device boxes or on outlet covers, or otherwise used in conjunction with wiring systems recognized by the National Electric Code.

Switch, isolating: A switch intended for isolating an electrical circuit from the source of power. It has no interrupting rating and is intended to be operated only after the circuit has been opened by some other means.

Switch, knife: A switch in which the circuit is closed by a moving blade engaging contact clips.

Switch-Leg: That part of a circuit run from a lighting outlet box where a luminaries or lamp holder is installed down to an outlet box that contains the wall switch that turns the light or other load on or off: it is a control leg of the branch circuit.

Switch, motor-circuit: A switch, rated in horsepower, capable of interrupting the maximum operating overload current of a motor of the same horsepower rating as the switch at the rated voltage.

Switch, transfer: A transfer switch is an automatic or non automatic device for transferring one or more load conductor connections from one power source to another.

Thermal Shock: Thermal shock is the effect of heat or cold applied at such a rate that non-uniform thermal expansion or contraction occur within a given material or combination of materials. In connectors, the effect can cause inserts and other insulation materials to pull away from metal parts.

Transformer: Equipment vital to the transmission and distribution of electricity designed to increase or decrease voltage.
The transformer was invented by Michael Faraday in 1831 to enable him to demonstrate the phenomenon of electro-magnetic induction. In a transformer, two coils of wire are wound on opposite sides of a metal core. When an electric current is passed into one coil, a transient electric current is induced in the other. By varying the number of windings round the coils, the voltage can be increased or decreased. Because induction is a transient phenomenon, the transformation can be repeated very quickly. Electrical substations are large transformers, and thus the device is key to efficient transmission of high voltage alternating current (AC).

Transmission Lines: Power lines normally used to carry high voltage electricity to substations which then is "stepped down" for distribution to individual customers.
Van de Graff generator: A machine for generating very high voltage static electricity. It uses a high speed belt rubbing against a hollow metal sphere, which acts as a capacitor. Modern uses include X-ray tubes and the acceleration of electrons for food sterilization. The generator was developed by American physicist Robert J. Van de Graff (1901-1966), who began work on it in 1929.

Volt: The unit of electrical potential difference and electromotive force equal to the difference of potential between two points in a conducting wire carrying a constant current of one ampere when the power dissipated between these two points is equal to one watt and equivalent to the potential difference across a resistance of one ohm when one ampere is flowing through it.

Voltage Drop: The loss of voltage between the input to a device and the output from a device due to the internal impedance or resistance of the device. In all electrical systems, the conductors should be sized so that the voltage drop never exceeds 3% for power, heating, and lighting loads or combinations of these. Furthermore, the maximum total voltage drop for conductors for feeders and branch circuits combined should never exceed 5%.

Watt: The watt (symbol: W) is the SI derived unit of power, equal to one joule of energy per second. That is, if 1 volt of potential difference is applied to a resistive load, and a current of 1 ampere flows, then 1 watt of power is dissipated.