Arcing Current passing (through air) across a gap, that is, using the air itself like a wire. Arc-fault interrupter A circuit breaker that can also trip for line-to-neutral arcing (which would not soon trip a standard breaker). Required for new bedroom circuits since 2002 and most rooms since 2008.

Breaker An automatic switching device that disconnects power to a circuit when current or heat exceeds a certain level for a certain amount of time. It clips on to one or two live busbars in a panel box and passes this liveness through itself to the circuit wire attached to it, normally by means of a screw. Its handle is generally in one of three positions: on, tripped (the middle position), and off.

Busbar A piece of rigid metal within a panel or fusebox which distributes electricity to the various circuits by means of their connection to it.

Circuit The actual or intended path of current between points of differing voltage. In the case of a household 120 volt circuit, the path is between a hot wire at the breaker and a neutral wire connected to the grounded neutral bar in the panel. In a sense each loop that current makes (through a single light, for instance) is a circuit, but the most common meaning is the "branch circuit", defined as everything fed (or interrupted) by a given breaker or fuse.

Common The terminal of a three-way switch (or the wire attached to it) which makes internal contact with one or the other of the traveler terminals, depending on the position the switch is moved to.

Dimmer Also rheostat. A switch able to dim its lights by altering the voltage it passes on. A dimmer normally gets warm when operating but will overheat if running more wattage than it is designed for.

Electricity A force generated onto loops of conductive material, transferred through their electrons, and applied as useful energy at parts of these loops.

Fusebox Like a panel, a usual main source of the circuits in a home. It contains fuses rather than breakers.

Fuse is a protective electrical
device. A fuse is rated for a maximum amount of current flow
which is measured in amps. Electrical current is measured in
amperes also called amps. When the current flow exceeds the
amperage rating on the fuse, the fuse link in the fuse will open
and stop the flow of current. Years ago everything, both AC and
DC current, were protected with fuses. Today most have been
replaced with electrical breakers

Ground The neutral wires of circuits and of the system are grounded, but a "ground wire" means a separate "grounding" wire keeping metal parts of devices, fixtures, or appliances from staying accidentally energized and endangering people or equipment. Installed in homes since the 1960's, these wires are to be either bare or green-covered.

Hot Or "live." Having electrical force (voltage) in relation to ground/earth, especially 120 volts. "Hot" is the termed used because anything even slightly connected to ground (such as a person) could get agitated as a path this force uses toward ground.

Jumper A short piece of wire within a box, going between two wirenuts or between two devices' terminals.

Junction box As distinguished from any electrical box, a box used only for making connections, not for also supporting a switch, receptacle, or light.

Outlet Any point along a circuit where a light or appliance receives its final connections to the hot and neutral of the circuit. The outlet may consist of a receptacle for a cord to plug into, or it may be a box at which the item using the electricity is "hard-wired". In practice, however, we usually mean a receptacle.

Overload When in its normal operation a circuit has carried a little too much flow a little too long, so that the wires will be getting too hot to be safe, the breaker will trip off. This is called an overload -- you were trying to run a bit too much at once on that circuit. You can now change your habits, plug one of those things into another circuit, let it happen again some other month, or have a new circuit installed for some of those things. So long as breakers do their job, overloading is not dangerous, just inconvenient. Safety people often warn us not to overload outlets or power strips, as if we know how to judge that. The two cases of this kind of "overloading" that need a little attention are light sockets and extension cords; just don't exceed their stated wattage or amperage. Compare "Short".

Panel Or "panel box" or "breaker box". The large metal box containing breakers for circuits. The "main" panel or "service" panel would be the central source for the home and would be receiving its power from the power company. There can be subpanels in a home, fed from the main panel and containing some of the home's circuit breakers. Some people still use the term "fusebox" to refer to a panel, but that term should relate to something having fuses. I suggest the term "panel" could refer to either a breaker box or a fusebox.

Pig Tail is a temporary electrical light device. The pig tail consists of a light socket and two connecting wires. There is normally one white wire and one black wire. These wires are connected to the primary wire hung to provide temporary lighting for a project. These wires are connected with wire nuts and taped with electrical tape for safety

Receptacle Also "plug-in"; or, loosely, "outlet" or "plug". A device that serves as the outlet for lights or appliances to connect to a circuit by means of a cord with a "plug" on the end.

Socket Also "lamp holder". The part of a light fixture that receives the bulb or tube. It is understandable that some people use "socket" to mean the receptacles we plug cords into, because in both cases the one thing is receiving the other thing that actually "uses up" electricity.

Switch A device used to interrupt continuity and current to part of a circuit. Terminal A screw or other pressure-device to which one or more wires are connected for passing electrical continuity and current along. Like a "Splice", but a terminal is anchored to a larger structure, whereas a splice is "free floating".

Wattage Rate of electric energy used by lights or appliances. When applied to devices, it indicates the maximum watts the device is designed to deliver or control (rather than use). Wattage is directly proportional to current and to voltage and is mathematically the product of them (amps times volts).