## Glossary of Electrical Terms

Make no mistake about it, even residential electrical systems are complex, combine that with all of the terms, jargon and acronyms and it would be tough for anyone new to the industry to grasp. If you’re just getting involved in electrical contracting, or are trying your hand at your own home project, it’s helpful to understand some of the basic terms used by electrician’s in the industry.

We’ve put together this handy electrical terms glossary that identifies some of the most common terms you’re likely to encounter as you get to work on your next construction or electrical project.

**Electrical Terms for Circuits**

**AC (Alternating Current):** An electric current that reverses its direction many times a second at regular intervals.

**DC (Direct Current):** An electric current that flows in only one direction.

**Feeder:** All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit over-current device.

**Fuse:** A circuit interrupting device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level. To restore service, the fuse must be replaced using a similar fuse with the same size and rating after correcting the cause of failure.

**Ground or Earth:** The reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.

**Ground Fault:** An unintentional, electrically conductive connection between an un-grounded conductor of an electrical circuit and the normally non–current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.

**Grounded Conductor:** A system or circuit conductor that is intentionally grounded.

**Grounded (Grounding):** Connected (connecting) to ground or to a conductive body that extends the ground connection.

**Ground-Fault Current Path:** An electrically conductive path from the point of a ground fault on a wiring system through normally non–current-carrying conductors, equipment, or the earth to the electrical supply source.

**Load:** Anything which consumes electrical energy, such as lights, transformers, heaters and electric motors.

**Neutral Conductor:** The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.

**Overload:** Operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated ampacity that, when it

persists for a sufficient length of time, would cause damage or dangerous overheating. A fault, such as a short circuit or ground fault, is not an overload.

**Parallel Circuit:** A circuit in which there are multiple paths for electricity to flow. Each load connected in a separate path receives the full circuit voltage, and the total circuit current is equal to the sum of the individual branch currents.

**Rectifier:** An electrical device that converts an alternating current into a direct one by allowing a current to flow through it in one direction only.

**Series Circuit:** A circuit in which there is only one path for electricity to flow. All of the current in the circuit must flow through all of the loads completing its path to the source of supply.

**Series Parallel Circuit:** An electric current containing groups of parallel connected receptive devices, the groups being arranged in the circuit in series; a series multiple circuit.

**Short Circuit:** A fault in an electric circuit or apparatus due usually to imperfect insulation, such that the current follows a by-path and inflicts damage or is wasted.

**Electrical Terms for Components**

**Ammeter:** Measures the current flow in amperes in a circuit. An ammeter is connected in series in the circuit (unless using a clamp-on ammeter)

**AFCI (Arc Fault Circuit Interrupter):** An arc fault circuit interrupter is a special type of receptacle or circuit breaker that opens the circuit when it detects a dangerous electrical arc. It’s used to prevent electrical fires.

**Capacitor:** A passive two-terminal electrical component used to store electrical energy temporarily in an electric field.

**Circuit:** A closed path in which electrons from a voltage or current source flow. Circuits can be in series, parallel, or in any combination of the two.

**Circuit Breaker:** An automatic device for stopping the flow of current in an electric circuit. To restore service, the circuit breaker must be reset (closed) after correcting the cause of the overload or failure.

**Conductor:** Any material where electric current can flow freely. Conductive materials, such as metals, have a relatively low resistance. Copper and aluminum wire are the most common conductors used in the electrical trade.

**DMM (Digital Multimeter):** A DMM is an electronic measurement tool that can measure voltage, current, resistance, capacitance, temperature, frequency

**Diode:** A semiconductor device with two terminals, typically allowing the flow of current in one direction only.

**Generator:** A device that converts mechanical energy to electrical energy for use in an external circuit. The source of mechanical energy may vary widely from a hand crank to an internal combustion engine. Generators provide nearly all of the power for electric power grids.

**GFCI (Ground Fault Circuit Interrupters):** A device intended for the protection of personnel 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 that required to operate the overcurrent protective device of the supply circuit.

**Inverter:** An apparatus that converts direct current into alternating current.

**Insulator:** Any material where electric current does not flow freely. Insulating materials, such as glass, rubber, air, and many plastics have a relatively high resistance. Insulators protect equipment and life from electric shock.

**Service:** The conductors and equipment used to deliver energy from the electrical supply system to the system being served.

**Service Lateral:** The underground service conductors between the street main – including risers – and the first point of connection to the service-entrance conductors in a terminal box, meter, or other enclosure.

**Semiconductor:** A solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects. Devices made of semiconductors, notably silicon, are essential components of most electronic circuits.

**SCR (Solid State Relay):** An electronic switching device that switches on or off when a small external voltage is applied across its control terminals. The switching action happens extremely fast.

**Solenoid:** A spiral of conducting wire, would so that when an electric current passes through it, its turns are nearly equivalent to a succession of parallel circuits, and it acquires magnetic properties similar to those of a bar magnet.

**Switch:** A device for making, breaking, or changing the connections in an electric current.

**Switchgear:** The combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream.

**Transistor:** A semiconductor device with three connections, capable of amplification in addition to rectification.

**Electrical Terms for Mathematical Calculations**

**Apparent Power:** Measured in volt-ampers (VA). Apparent power is the product of the rms voltage and the rms current.

**Ampere (A):** A unit of measure for the intensity of an electric current flowing in a circuit. One ampere is equal to a current flow of one coulomb per second.

**Capacitance:** The ability of a body to store an electrical charge. Measured in farads as the ratio of the electric charge of the object (Q, measured in coulombs) to the voltage across the object (V, measured in volts).

**Current (I):** The flow of an electric charge through a conductor. An electric current can be compared to the flow of water in a pipe. Measured in amperes.

**Demand:** The average value of power or related quantity over a specified period of time.

**Farad:** A unit of measure for capacitance. One farad is equal to one coulomb per volt.

**Frequency:** The number of cycles per second. Measured in Hertz. If a current completes one cycle per second, then the frequency is 1 Hz; 60 cycles per second equals 60 Hz.

**Henry:** A unit of measure for inductance. If the rate of change of current in a circuit is one ampere per second and the resulting electromotive force is one volt, then the inductance of the circuit is one henry.

**Hertz:** A unit of measure for frequency. Replacing the earlier term of cycle per second (cps).

**Impedance (Z):** The effective resistance of an electric circuit or component to alternating current (AC), rising from the combined effects of ohmic resistance and reactance.

**Inductance (H):** The property of a conductor by which a change in current flowing through it induces (creates) a voltage (electromotive force) in both the conductor itself (self-inductance) and in any nearby conductors (mutual inductance). Measured in henry (H).

**Kilowatt-hour (kWh):** The product of power in kW and time in hours. Equal to 1000 Watt-hours. For example, if a 100W light bulb is used for 4 hours, 0.4kWhs of energy will be used (100W x 1kW / 1000 Watts x 4 hours). Electrical energy is sold in units of kWh.

**Kilowatt-hour Meter:** A device used to measure electrical energy use.

**Kilowatt (kW):** Equal to 1000 watts.

**Ohm:** (Ω) A unit of measure of resistance. One ohm is equivalent to the resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt.

**Ohm’s Law:** The mathematical equation that explains the relationship between current, voltage, and resistance (V=IR).

**Power:** The rate at which electrical energy is transferred by an electric circuit. Measured in Watts.

**Reactive Power:** The portion of electricity that establishes and sustains the electric and magnetic fields of AC equipment. Exists in an AC circuit when the current and voltage are not in phase. Measured in VARS.

**Resistance (Ω Ohms):** The opposition to the passage of an electric current. Electrical resistance can be compared to the friction experienced by water when flowing through a pipe. Measured in ohms.

**True Power:** Measured in Watts. The power manifested in tangible form such as electromagnetic radiation, acoustic waves, or mechanical phenomena. In a direct current (DC) circuit, or in an alternating current (AC) circuit whose impedance is a pure resistance, the voltage and current are in phase.

**VARS:** A unit of measure of reactive power. Vars may be considered as either the imaginary part of apparent power, or the power flowing into a reactive load, where voltage and current are specified in volts and amperes.

**Volt-Ampere (VA):** A unit of measure of apparent power. It is the product of the rms voltage and the rms current.

**Volt (V):** A unit measure of voltage. One volt is equal to the difference of potential that would drive one ampere of current against one ohm resistance.

**Voltage (E):** An electromotive force or “pressure” that causes electrons to flow and can be compared to water pressure which causes water to flow in a pipe. Measured in volts.

**Watt-hour (Wh):** A unit of electrical energy equivalent to a power consumption of one watt for one hour.

**Watt (W):** A unit of electrical power. One watt is equivalent to one joule per second, corresponding to the power in an electric circuit in which the potential difference is one volt and the current one ampere.

**Electrical Terms for Conduit Bending**

**Hand Bender:** A tool used for bending EMT (electrical metal tubing), IMC (intermediate metal conduit), and RMC (rigid metal conduit). hand benders come in sizes: 1/2″, 3/4″, 1″, and 1-1/4″

**Four Bend Saddle:** Four bends in a piece of conduit that clears and obstacle by saddling it.

**Offset:** A bend in conduit to clear an obstacle. Typically only two bends.

**Three Bend Saddle:** Three bends in a piece of conduit – one in the center and two side bends that clear an obstacle by “saddling” it.

**Gain: ** The difference between the sum of the straight distances and the actual length of conduit (how much the conduit will grow after being bent).

**Shrink:** The amount the conduit will “shrink” because of bending around an obstruction – picture an inch worm and how it shrinks when it moves. Shrink is added to the over all distance to the obstruction to compensate before bending.

**Multiplier:** Used to calculate the distance between bends using “multiplier X offset”

**Random Electrical Terms That You Should Be Familiar With**

**Arc Flash:** An arc flash is light and heat and is a type of electrical explosion or discharge that results from a low-impedance connection through air to ground or another voltage phase in an electrical system. Arc flash temperatures can reach or exceed 35,000 °F

**Arc Blast:** The intense heat from an arc causes sudden expansion of air resulting in a blast. Copper expands during an arc flash event at a factor of 67000 times within a few milliseconds.

**Calorie:** The French heat unit. Used to measure energy levels for Arc Flash boundaries and proper PPE when working on energized electrical equipment.

**CE (Construction Electrician):** Construction electricians can perform those basic tasks with little or no supervision, though they can’t act as a foreman or supervise other workers.

**Experts you Can Trust**

Price is important, but when choosing an electrician judge the entire picture an electrician is showing you character, expertise, the ease of working with him or her, and overall value. A large part of an electrician’s value is that he/she gets the job done right and safely without taking too much of your time and inconveniencing you. A very competent electrician can save you money by suggesting more efficient ways to do a job or to save on electricity. When you enjoy a good relationship with your electrician, it can save you both time and money. Give us a call about your next electrical project and we will be happy to help.