Amp
(Ampere)
A unit that measures the strength/rate of flow of electrical
current.
Armored
Cable
Electrical wires protected by metal sheathing.
Branch
Circuits
The circuits in a house that branch from the service panel to
boxes and devices.
Breaker
A switch-like device that connects/disconnects power to a
circuit.
Buss
Bar (also Bus Bar)
Separate, metallic strips that extend through the service panel.
Breakers slide onto the "hot" busses and neutral and
ground wires screw down in their respective busses.
BX
Cable
An old type of armored cable now illegal.
Cable
Clamps
Metal clips inside an electrical box that hold wires in place.
Circuit
A continuous loop of current (i.e. incoming "hot"
wire, through a device, and returned by "neutral" wire).
Circuit
Breaker
The most common type of "overcurrent protection." A
breaker trips when a circuit becomes overloaded or shorts out.
Conduit
A protective metal tube that wires run through.
Duplex
Receptacle
The commonly used receptacle (outlet). Called "duplex"
because it has two plug-in sockets.
Fuses
Removable devices that link a circuit at the fuse box. Fuse
connections blow apart and break the circuit if an overload or short
occurs.
Fixture
Any permanently connected light or other electrical device that
consumes power.
GFCI
or GFI (Ground Fault Circuit Interrupter)
A specific type of circuit protection (commonly required in
kitchens & bathrooms) that helps safeguard against shocks. GFCI
protection can come from an outlet or a breaker.
Ground
Fault
Current misdirected from the hot (or neutral) lead to a ground
wire, box, or conductor.
Hot,
Neutral, Ground
The three most common circuit wires. The hot brings the current
flow in, the neutral returns it to the source, and the ground is a
safety route for returning current. The ground and neutral are
joined only at the main service panel.
Junction
(Electrical) Box
A square, octagonal, or rectangular plastic or metal box that
fastens to framing and houses wires, and/or receptacles and/or
switches.
Knockout
A removable piece of an electrical box or panel that's
"knocked out" to allow cable to enter the box.
Lead
The short length of a conductor that hangs free in a box or
service panel. (i.e. a wire end)
NM
Nonmetallic-sheathed (plastic).
NMC
Solid plastic nonmetallic-sheathing used in wet or corrosive
areas, but not underground (see UF).
Ohm
A unit that measures the resistance a conductor has to
electricity.
Pigtail
A short, added piece of wire connected by a wire nut. Commonly
used to extend or connect wires in a box.
Romex
A brand name of nonmetallic-sheathed cable made by General Cable
Corporation. Often mistakenly used as a collective term for NM
sheathed cable.
Rough-In
Installing the boxes, cables, and making "in-wall"
connections while the walls are still open. Later, final connections
are made and the devices and appliances are installed during the
trim-out.
Service
Entrance (SE)
The location where the incoming electrical line enters the home.
Service/Supply
Leads
The incoming electrical lines that supply power to the service
panel.
Service
Panel
The main circuit breaker panel (or fuse box) where all the
circuits tie into the incoming electrical supply line.
Short
Circuit
When current flows "short" of reaching a device.
Caused by a hot conductor accidentally contacting a neutral or
ground. A short circuit is an immediate fault to ground and should
always cause the breaker to trip or the fuse to blow. (also see
ground fault)
Travelers
Wires that carry current between three-way and/or four-way
switches.
UF
(Underground Feeder) cable
Cable designed and rated for underground, outdoor use. Cable
wires are molded into solid plastic.
Volt
A unit that measures the amount of electrical pressure.
Watt
A unit that measures the amount of electrical power.
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