Electrical terms, explained for beginners

Plain-English definitions from official sources · Last reviewed October 12, 2026

A

alternating current

Alternating current (AC) is electric current that reverses direction at regular intervals. It's the kind of electricity that powers the appliances in your home. Transformers change the voltage of AC. Its opposite is direct current. [18][25][29]

ampere

Also called: amps, amperes, amperage

An ampere (amp) is the unit of electric current: how much electricity flows through a circuit. One volt pushing through one ohm of resistance makes one amp. Wires, breakers and electrical services are rated in amps. A wire's ampacity is the current it can carry continuously without getting too hot. [24][25]

arc flash

An arc flash happens when electricity jumps through the air, making an electric arc. The high temperatures of an arc near your body can cause serious burns. Protecting workers from arc flash is a main goal of NFPA 70E. [6][26]

B

branch circuit

Also called: branch circuits

A branch circuit is the wiring between the last overcurrent device (the breaker or fuse in the panel) and the outlets it serves. [24]

C

circuit breaker

Also called: circuit breakers, breaker, breakers

A circuit breaker is a switch that you can turn on and off by hand and that also opens (trips) automatically when too much current flows. Fuses do the same job by melting. Both protect wires and equipment from overheating. Breakers are one kind of overcurrent protection. [24][26]

code cycle

Also called: code edition, code cycles

The NEC (National Electrical Code) is revised on a three-year cycle, and each version is called an edition: 2017, 2020, 2023 and 2026 are recent ones. Texas law, for example, tells the state to adopt each revised NEC after the NFPA (National Fire Protection Association) publishes it "every three years."

Why it matters to you: states adopt new editions on their own schedule, so the edition in force (and the one your exam is based on) depends on your state, and the two can differ. Arkansas's rule adopts the 2026 edition, while Michigan's exam bulletin says its questions are based on the 2023 edition. Before you buy a code book or study for an exam, check which edition your state's exam bulletin names. License renewal courses often cover code changes. [1][2][3][4][9]

conduit

Also called: conduits

Conduit is metal or plastic tubing that protects electrical wires. It's one type of raceway; common kinds include rigid metal conduit and flexible conduit. Electricians use conduit benders to shape it so it runs neatly around corners. [1][24]

D

direct current

Direct current (DC) flows in one direction only. Solar panels produce it. In a solar system, other equipment takes the DC from the panels and converts it to the alternating current used by appliances. [18]

E

electrical circuit

Also called: electrical circuits

A circuit is a complete path that electricity flows around: from the source, through wires and a device such as a light bulb, and back. Turning a switch off opens the circuit and stops the flow; turning it on closes the circuit. If your body becomes part of a circuit, you get a shock. [26][30][31]

electrical contractor

An electrical contractor is a business that installs, alters, repairs or maintains electrical wiring for customers. Some states license the business separately from the electricians' personal licenses. Texas, for example, requires the contractor to be a master electrician or employ one. About two-thirds of electricians (66%) work for electrical contractors. [1][3][15]

electrical inspector

Also called: electrical inspectors

An electrical inspector examines a building's installed electrical systems to make sure they meet the code and work properly. That includes wiring, lighting, sound and security systems, solar systems and generators. [21]

electrical service

Also called: service entrance

The electrical service is the wiring and equipment that deliver power from the utility to a building's wiring system. The service equipment, usually the main breaker or switch and fuses, is the main control and cutoff for the whole building. Michigan's exam bulletin, for example, lists "services" as an exam topic. [9][24]

electrical theory

Electrical theory is how electricity behaves: voltage, current, resistance, power and how circuits work, including Ohm's law. It's one of the main classroom subjects for apprentices, along with blueprint reading, math, the electrical code and safety. Licensing exams include theory questions too. [1][9][22]

Electrical Training Alliance

Also called: electrical training ALLIANCE

The Electrical Training Alliance, formerly called the NJATC (National Joint Apprenticeship and Training Committee), is the joint training program of NECA and the IBEW. It sets national standards for picking and training apprentices and writes the course materials that local union programs use. It says it has trained over 350,000 apprentices to journeyman level.

Its training center locator finds the local program (JATC) near you. Its programs cover four kinds of work: outside lineman, inside wireman, installer technician and residential wireman. More on applying: electrician apprenticeships and apprenticeship aptitude tests. [12][13]

F

feeder

A feeder is the wiring that carries power from the service equipment (or another power source) to the panel where the final branch-circuit breakers are. Feeders are a licensing exam topic; Michigan's exam bulletin lists them, for example. [9][24]

fire alarm technician

Also called: fire alarm specialty technician

A fire alarm technician installs and works on fire alarm systems, which detect fire or smoke in a building and sound the alarm. Some states license it as its own specialty. Michigan, for example, defines a fire alarm specialty technician as someone mainly engaged in "the design and practical installation or alteration of fire alarm systems." The work follows NFPA 72 as well as the NEC. Apprentices may get some fire alarm training in class too. [1][7][15]

G

grounding and bonding

Also called: grounding

Grounding means connecting an electrical system or equipment to the earth (or something that serves as the earth) through a low-resistance path. It keeps dangerous voltage from building up, and current flowing to ground can trip the circuit protection devices.

Bonding means permanently joining metal parts so they form one continuous electrical path that can safely carry any current likely to flow. Together they keep metal boxes, pipes and equipment from becoming "hot" and shocking someone. Grounding and bonding is the first topic on Michigan's exam topic list, for example. [9][24][26]

I

IEC (Independent Electrical Contractors)

Independent Electrical Contractors is a nonprofit trade association of electrical contractors, founded in 1957. It speaks for the "open shop" or "merit shop" side of the industry. IEC says it has 54 educational campuses and local chapters and trains more than 20,000 electrical apprentices a year. Many state pages on this site list the IEC chapters near you as one apprenticeship route. See union vs. non-union. [14]

inside wireman

Also called: inside wiremen

Inside wireman is the union apprenticeship track for electricians who install power, lighting, controls and other electrical equipment in commercial and industrial buildings. When a program says "inside," it means building work, as opposed to outside utility line work (see lineman). [13]

IBEW (International Brotherhood of Electrical Workers)

The IBEW is a labor union founded in 1891 in St. Louis. It says it represents about 901,000 active members and retirees in the United States and Canada, in construction, utilities, telecommunications, manufacturing and other fields. For a beginner, the IBEW matters because, together with contractors in NECA, it runs union apprenticeship programs through local joint apprenticeship training committees (JATCs) and the Electrical Training Alliance. See union vs. non-union for how this route compares with open-shop programs. [10][11][12][13]

J

journeyman electrician

Also called: journeyman electricians, journey worker electrician

A journeyman electrician has finished training and may work on their own, subject to state or local licensing. Michigan's law describes the job as being "engaged in the practical installation or alteration of electrical wiring." In licensed states you usually need a set number of supervised work hours plus an exam. Texas, for example, requires 8,000 hours of on-the-job training under a master electrician and a journeyman exam. See what is a journeyman. [1][3][15]

L

lineman

Also called: linemen, line installer, line worker, power line installer

A lineman (also called a line installer or line worker) installs and repairs the cables and wires of the power grid: the transmission and distribution lines that carry power from the plant to homes and businesses. The work involves high voltage and heights. Training is usually an apprenticeship or employer program of up to 3 years, sometimes run jointly by the employer and the union. A few states license linemen; Minnesota, for example, defines a lineman as someone who builds and maintains utility transmission and distribution systems. [13][16][17]

load calculation

Also called: load calculations, load calc

A load calculation adds up the power a building's lights, outlets and appliances will draw, using the electrical code's rules, to choose the size of the electrical service, panel and wires. Building departments may ask for one with a permit; the City of Auburn, California's worksheet calls it the method "for determining the electrical load and sizing of the electrical service." Michigan's exam bulletin, for example, lists load calculations as an exam topic. [9][32]

low-voltage work

Also called: low-voltage, low voltage, limited energy, limited-energy, power limited, power-limited

Low-voltage (also called limited-energy or power-limited) work is wiring for systems that run on small amounts of power: alarms, telephones, computer networks, video, security and access control. The NEC groups many of these limited-energy systems in its Chapter 7.

Some states license this work separately; Minnesota, for example, has a power limited technician license. The union apprenticeship for it is the installer technician track. [2][13][17]

M

maintenance electrician

Also called: maintenance electricians

A maintenance electrician keeps existing electrical wiring and equipment working: fixing or replacing parts, light fixtures, controls and motors. Some states have a separate license for this work; Minnesota defines a maintenance electrician as someone qualified "to properly maintain and repair electrical wiring, apparatus, and equipment." [1][17]

master electrician

Also called: master electricians

A master electrician is the level above journeyman. Journey workers who meet more requirements may become masters. In Texas, for example, a master needs 12,000 hours of on-the-job training, at least two years holding a journeyman license and a master exam. A Texas master may do all electrical work and supervise other electricians. See journeyman vs. master. [1][3]

motor controls

Also called: motor control

Motor controls are the devices that start, stop and protect electric motors. Electricians install and repair control systems in homes, businesses and factories, and maintenance work can include fixing motors. "Motors and motor controls" is on Michigan's exam topic list, for example. [1][9]

N

NEC (National Electrical Code)

The National Electrical Code, also called NFPA 70, is the rulebook for safe electrical design, installation and inspection. It is published by the National Fire Protection Association (NFPA), which says it is "enforced in all 50 states." It isn't a law by itself: a state or city adopts it as its electrical code.

You'll run into the NEC everywhere. Electricians follow state and local rules based on it, apprentices study it in class, and licensing exams have questions on the NEC and on state and local codes. Some exams are open book, so you learn to find answers in the code book fast. A new edition comes out every three years (see code cycle). [1][2][3]

NFPA 70 (National Electrical Code)

NFPA 70 is the National Fire Protection Association's number for the National Electrical Code. Exam bulletins and state rules often use both names, for example "the National Electrical Code (NFPA 70), 2026" in Arkansas's rule. They mean the same book. [2][4]

NECA (National Electrical Contractors Association)

NECA is an association of electrical contracting businesses. Its link to apprenticeships: NECA and the IBEW created a joint training program, now called the Electrical Training Alliance, and run hundreds of local apprenticeship programs together. That's why you'll see union programs described as "IBEW/NECA" programs. [12]

NFPA 72 (National Fire Alarm and Signaling Code)

The National Fire Alarm and Signaling Code (NFPA 72) covers fire detection, fire alarm systems and emergency communications, including mass notification systems. If you go into fire alarm work (see fire alarm technician), you'll use it alongside the NEC. [7]

NFPA (National Fire Protection Association)

The National Fire Protection Association is a self-funded nonprofit, working on safety since 1896, that publishes more than 300 codes and standards on fire, electrical and related hazards. For electricians, its most important documents are NFPA 70 (the National Electrical Code), NFPA 70E (electrical safety at work) and NFPA 72 (fire alarms). [2][5][6][7]

NJATC (National Joint Apprenticeship and Training Committee)

NJATC is the former name of the Electrical Training Alliance, the national IBEW/NECA training program. You'll still see the old name in some places, for example "NJATC aptitude test" in some local programs' requirements on our state pages. [12]

NABCEP (North American Board of Certified Energy Practitioners)

NABCEP is a nonprofit, founded in 2002, that certifies solar and other renewable energy workers. Its best-known credential is the PV (photovoltaic) Installation Professional board certification, and it also has entry-level "associate" credentials for people new to the field. More on solar careers: our solar installer guide. [20]

O

ohm

Also called: ohms, Ohm's law, resistance

An ohm is the unit of electrical resistance: how much a material resists the flow of current. Metals have low resistance and are called conductors; glass, plastic and rubber resist it strongly and are called insulators.

Ohm's law ties the units together: current in amps equals voltage in volts divided by resistance in ohms. It's a basic part of electrical theory, which apprentices study in class. [22][26]

open-book exam

Also called: open book

Many licensing exams are open book: you may use listed reference books during the test. For electricians that usually means the National Electrical Code. Michigan's bulletin, for example, says "The examination is OPEN BOOK" and lists the NEC and the state's own electrical rules as allowed references. The rules on what you may bring, and whether the book can have tabs or notes, differ by exam, so read your state's candidate bulletin. [9]

overcurrent protection

Also called: overcurrent

Overcurrent is any current higher than a wire or piece of equipment is rated for. It can come from an overload, a short circuit or a ground fault. Overcurrent protection means the fuses and breakers that cut the power before wires overheat. Overcurrent protection is a licensing exam topic; Michigan's exam bulletin lists it, for example. [9][24][26]

P

panelboard

Also called: electrical panel, service panel, breaker panel, breaker box

A panelboard, usually called the electrical panel or breaker box, is a panel holding the circuit breakers or other overcurrent devices that control light, heat and power circuits. It's mounted in a cabinet in or against a wall. [24]

PV (photovoltaic)

Photovoltaic (PV) panels turn sunlight into electricity. Single cells are joined into modules (panels), and panels are joined into arrays. They make direct current (DC), which other equipment converts to the alternating current (AC) your home uses.

PV installers mount and maintain solar systems. Depending on the job and state law, the installers may connect the panels to the grid, although electricians sometimes do that part. Electricians may also earn solar certifications such as NABCEP. See our solar installer guide. [1][18][19]

R

raceway

Also called: raceways

A raceway is an enclosed channel of metal or plastic made to hold wires and cables. Conduit is one kind. Michigan's exam bulletin, for example, lists "box and raceway fill" (how many wires may go in a box or raceway) as an exam topic. [9][24]

residential wireman

Also called: residential wiremen

A residential wireman specializes in the wiring of houses and apartment buildings. It's a separate apprenticeship track at the Electrical Training Alliance, and some states issue a license for it. In Texas, a residential wireman may only do electrical installations in single-family and multifamily homes of up to four stories. [3][13]

S

sign electrician

Also called: sign electricians

A sign electrician builds, installs and services electric signs: lighted signs, neon and outline lighting. Texas has a separate ladder for it (journeyman and master sign electrician, each with 8,000 or 12,000 hours under a master sign electrician plus an exam). Michigan's law defines an electric sign to include outline lighting. [3][15]

NFPA 70E (Standard for Electrical Safety in the Workplace)

The Standard for Electrical Safety in the Workplace (NFPA 70E) sets safe work practices to protect workers from shock, electrocution, arc flash and arc blast. The NFPA says it was first developed at the request of OSHA (the federal workplace safety agency) and helps with complying with OSHA's electrical rules.

The NEC is about how wiring must be installed; NFPA 70E is about how you stay safe while you work. Some licensing exams cover both: California's electrician certification exam, for example, provides the 2023 NEC and the 2024 NFPA 70E on screen. [6][8]

T

transformer

Also called: transformers

A transformer changes the voltage of alternating current. Utilities use transformers to step voltage up for long-distance power lines and down for homes and businesses. Inspecting transformers is one of the duties the BLS (Bureau of Labor Statistics) lists for electricians. [1][29][30]

V

volt

Also called: volts, voltage

A volt is the unit of electric "pressure": the push that drives current through a wire. Voltage is the difference in that pressure between two wires, or between a wire and ground. Circuits are described by their nominal voltage, such as 120/240 volts or 600 volts. [22][23][24]

W

watt

Also called: watts, kilowatt, kilowatts

A watt is the unit of electrical power, equal to one amp at one volt. A kilowatt (kW) is 1,000 watts. Electricity used over time is measured in watt-hours; utilities bill in kilowatt-hours (kWh), one kilowatt used for one hour. [27][28]

wiring methods

Wiring methods are the approved ways to run electrical wiring, such as cable or wire in conduit, and the rules for where each may be used. Federal OSHA (Occupational Safety and Health Administration) workplace rules have a section on them, and "wiring methods and installations" is on Michigan's exam topic list, for example. [9][33]