Electric Glossary for the Homeowner - Circuits, Currents and Measurements

Everything seems to have its own jargon, and electricity is no exception. Here are some commonly used terms you’re likely to come across. Knowing them will make you a better-informed customer when it comes time for electrical work and buying electric appliances.

AC (alternating current)

Electrical current can flow in a single direction (direct current) or change direction (polarity) at regular intervals (cycles). Alternating current is preferred for distribution networks because it can be transmitted efficiently at high voltages and stepped down by transformers for safer use in the home. Common AC home voltages in the US are 110/120 and 220/240. Alternating current can be changed to direct current with a converter. 

Amp (Ampere)(A)

Amperes are the measurement of the flow of electrons and, in combination with voltage, tell how much energy can be delivered on an electrical circuit. Think of amps as the intensity of the flow and volts as the pressure behind it.


A compact fluorescent lamp designed for use in standard light bulb bases. CFLs use less energy than tungsten-filament bulbs and give off less heat. They contain mercury and other toxic substances, though, which can be released if the bulb is broken, and they must be disposed of properly. 


A circuit is a closed path from the source of energy through the conductors and then back to the energy source. “Short” circuits occur when that path is interrupted and can result in serious shock hazards. 

Circuit Breaker/Fuse

A circuit breaker is a protective device similar to a switch that shuts off when a predetermined amount of load on a circuit is exceeded. Older home systems used fuses containing metallic strips that would melt and break the circuit’s flow instead of “tripping” like a circuit breaker. Some things—Christmas light strings, for instance—still use fuses that must be replaced when they “blow.” 

Coaxial Cables (Coax)

Coaxial cables are specially designed wires with conductors and shielding to deliver radio-frequency (RF) signals such as television, computer, and digital audio efficiently and without interference from other RF signals in the air. 


Any substance that is able to transfer electricity. Ideally, electric current in your home will be confined to insulated conductors (wiring) designed for that purpose, but other things like moisture and bare metals are conductors, too, and can present serious hazards if stray current reaches them. 

Direct Current (DC) 

Current that flows in a single direction, such as from one pole of a battery to another. Direct current can be converted to alternating current (AC) with a device called an inverter. 

Data Cable

Cable that transfers data such as Ethernet computer data, telephone signals, or USB signals. Different types of data may require specific types of cable that are generally identified by a category number, such as Cat 5 and Cat 6 for Ethernet connections. 

GFCI (Ground Fault Circuit Interrupter)

A type of circuit breaker that detects minute current leaks (ground faults) and interrupts their flow. It protects areas where electric shocks present special hazards such as bathrooms, kitchens, garages, and outdoor outlets. Most building codes require GFCI outlets in those locations. 

Ground, Ground Wire

A conductor added to electrical circuits to safely guide stray or excessive current to the earth where it is dissipated. Often referred to simply as “earth.” 

Kilowatt-hour (KWH)

A measure of energy usage in thousands of watts used in one hour (see Watts, below). 


A light emitting diode consisting of a crystal that gives off a certain color of light when energized with electricity. LED lights have a much longer life span and use less power than standard light bulbs, thus are more economical. 

Ohm (O)

The unit of measurement of the electrical resistance of a conductor. The resistance of a wire increases as it becomes longer and decreases as it becomes wider. Think of it as friction in a hose; a long, narrow hose delivers water more slowly than a short, wide one. 

Photovoltaic (PV) Energy

Energy produced by a radiant source like the sun that is converted into electricity that can be used directlyorstored for future use. 

Surge Protector

A device that detects spikes in line voltage and limitsit by either blocking or grounding voltages above a safe threshold for equipment on that circuit. 


A device used for reducing or increasingvoltage. Not to be confused with converters or inverters that change current from AC to DC or vice versa. They can range from huge ones on power lines to small devices used to convert household current to 12- or 24 low-voltage circuits. 

Volt (V)

The unit of measurement for electrical pressure. 

Watt (W)

The unit of measurement for power of a current (the amount of work it can do). It is calculated by dividing volts by amps. Power companies charge for electrical use in kilowatts (1000 watts) used.

The pros at Allstar Electrical have served the Front Range for over 15 years and are top-rated by the BBB and Angie’s List. We offer homeowners, builders and businesses reliable, professional workthat is safe and up to code.Whatever your needs may be, call Allstar Electrical at 303.399.7420 or visit our website. Then use our handy on-line forms to request an estimate or set up an appointment.

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