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110 Voltage
An older term for the nominal voltage for lights and portable appliances in homes. "120" would be a more accurate and up-to-date identification of this voltage.
220 Voltage
An older term for the nominal voltage in a home for running some major appliances. "240" would be a more accurate and up-to-date identification of this voltage. Dual voltage is available to homes and businesses (120/240).
Appliance
A non-lighting item which consumes electricity by resistance rather than just passing it on. (An appliance is not a lighting fixture nor a device such as a fax machine, garbage disposal, even a wired-in smoke alarm)
Arcing
Current passing (through air) across a gap, using the air itself like a wire.
Arc-fault interrupter
A circuit breaker (or receptacle) that can trip off for line-to-neutral arcing (which would not soon trip a standard breaker) or also for in-line (series) arcing. Required for new bedroom circuits since 2002 and most rooms of new houses since 2008. See AFCI.
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(s) attached to it, normally by means of a screw(s). 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.
Cable
Compare "Wire". A cable is a set of wires, usually encased in an outer protective sheath. A "cord" would be a cable by this definition so far, but a cable is part of a permanent installation; a cord is more flexible and often has a plug end for a portable appliance or lamp. "2-wire cable," such as 14-2 and 12-2 (which indicate wire size) refers to a cable with two insulated wires, not counting any ground wire. Likewise 3-wire cable has three insulated wires, with any ground being additional.
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.
current
The flow of electrons in a wire (or other conductor). This is measured in amps (amperes). Because a house is provided with alternating current, the terms "positive" and "negative" do not apply as they do to direct current in batteries, cars, and such. Instead, in the case of 120-volt power, the power company is providing electricity that flows "to" their neutral wire "from" hot wire. This directional talk sounds misleading, since the actual electrons are moving back and forth sixty times per second. Similar to a roadway from one town to the next, though the highway simply goes between them and doesn't start at one or the other.
Device
As distinct from a fixture or appliance, an item which does not itself consume significant electricity, but interrupts or passes it on in a particular fashion. For example, a switch, a receptacle, a thermostat, a breaker, a fuse.
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. Also tame electricity.
Fixture
Or luminaire. A non-portable electrically-produced-light assembly. Distinguished from appliance or device.
Fuse
A device that interrupts current to its circuit by melting apart. Then it must then be replaced.
Fusebox
Like a panel, a usual main source of the circuits in a home. It contains fuses rather than breakers.
Gang
A combining of more than one device side-by-side, as, a "three-gang" switch box.
GFI or GFCI
A ground-fault interrupter. A device to prevent electrocution, which serves also as a receptacle or (less commonly) as a breaker. The letters "GFCI" stand for "ground-fault circuit interrupter" and the word "circuit" is rather vague. "GFI" clearly states the function it performs: "ground-fault interrupter". Since 1973 Code has required GFI protection for more and more receptacle locations in homes. If connected to properly, a GFI receptacle is also able to sense and disrupt ground-faults at any standard receptacles wired on from it.
Ground
The common reference point for the voltage of a home's electrical system. It refers to an intended or unintended connectedness to the earth. 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. The ground wire is not connected as part of the normal path of the circuit, as a neutral is. When a ground wire does carry current, it is taking care of an otherwise dangerous situation; in fact, it is supposed to carry so much flow suddenly, that it causes the breaker of the circuit to trip and alerts us of a problem which requires attention. Without a ground, our bodies would more frequently be a path for current from a hot wire touching the metal to get to ground (without our having enough conductivity to trip a normal breaker!).
Ground-fault
Any short circuit finding at least some of its path to the earth by way of something other than the neutral wire. It is a "leaking" of current off of the intended path which may produce a shock.
Hot
Also "live." As an adjective - having electrical force (voltage) in relation to ground/earth, especially 120 volts. "Hot" is the term used because anything even slightly connected to ground (like us!) could get agitated as a path this force uses toward ground. As a noun - the wire/terminal/contact that is to be hot, especially the wire from a breaker to lights/appliances.
Hotness
Having voltage in relation to ground, especially 120 volts.
Jumper
A short piece of wire within a box, going between two wirenuts or between two devices' terminals. It passes a function (hot, switched, neutral) from the one place to the other. A pigtail does this too, but only goes from a wirenut to a device or fixture wire.
Junction box
As distinguished from any electrical box, a box used only for making connections, not for also supporting a switch, receptacle, or light. The boxes for these others usually also have connections and splices in them in addition.
Line and Load
Relative terms. In relation to a given switch or device, line refers to wires or voltage being "supplied" to it from "upstream" or from the direction of the main service panel. With regard to the same device, load refers to wires (or terminals) that are "downstream" from or controlled by it. So wires from a switch or GFI might be load wires with respect to that switch but line wires with respect to another switch downstream from it.
Another use of the term "load" is to refer to the energy "user(s)" along the circuit's path, such as a light or appliance. By providing resistance, these items limit current and in the process do useful things.
Another use of the term "load" is to refer to the energy "user(s)" along the circuit's path, such as a light or appliance. By providing resistance, these items limit current and in the process do useful things.
Neutral
The white wires of a circuit that carry current "back" from a light or appliance. Contact with them should not normally shock because they are normally connected to ground.
Open Outlet
A physical discontinuity at some point along the path of some part of a circuit. Unlike an overload or short, an open involves current no longer being able to flow. This might be intentional, as when we turn a switch off. Regarding troubleshooting, an open is typically a break, gap, or deterioration. For instance, a wire has become too loose at the terminals on a receptacle or at a wire connector. It is hard to think of a gap like this as "opening" the circuit, since it seems like it has the effect of closing it down.
Outlet
Technically, 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, a receptacle. A switch, breaker or junction box are not outlets.
Overload
When in its normal operation a circuit has carried a little too much flow a little too long, the wires will get too hot to be safe and the breaker will trip off. This is called an overload -- too much at once on that circuit. You can plug one of those things into another circuit, let it happen again or have a new circuit installed to avoid this situation. As breakers do their job, overloading is not dangerous, just inconvenient. Safety people often warn us not to overload outlets or power strips for this reason - how to know you are overloading? Overloading which requires attention are light sockets and extension cords; don't exceed their stated wattage or amperage.
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. However, fusebox is term related to something with fuses. A panel could refer to a breaker box or a fusebox.
Pigtailing
To provide circuit connection to a fixture, appliance, or device by means of a single wire (the pigtail) getting its own connection out of a connector (wire "nut") that contains other wires of the circuit. Other ways of connecting would be for incoming and outgoing circuit wires to connect directly to the device's terminals or the fixture's wires.
Phantom voltage
An inconsequential voltage many testers will detect. It may register as a lower or a full voltage found on a wire that is connected neither to hot nor to neutral/ground. It seems to come about by means of capacitance or inductance from a hot wire that is near the unconnected wire over a good distance in the same cable. Not to be confused with "phantom load," which is the consumption of electricity by a TV when it is plugged in but not turned on, or a charger when it is plugged in but not charging anything.
Receptacle
Also plug-in, 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.
Short
A short circuit or ground-fault. A short is an unintended continuity from a hot wire to something of different voltage. In a 240-volt circuit a possible short would involve both hot wires touching (rare). All other shorts in a home will tend to be from the hot to ground by way of the neutral wire or (less technically) the ground wire or anything that provides a path to the earth. A short will not trip a breaker if its path has quite a bit of resistance. A short is something other than an overload that can trip a breaker, and for quite a different reason. With a short the flow of current is not due to the intended, limited use of electricity through lights and appliances, but is due to a potentially huge flow of electric power by way of an unintended and (often) very conductive path. Current still flows around from the ungrounded starting point to the grounded end point, and so it is still technically going in a "circuit". But it is not the intended circuit, which would be limited and safe by design.
For instance; if the hot wire at a light fixture made contact with the metal of the fixture, which is grounded by a ground wire, sends a lot of current along this path can trip the breaker off. A "short" is understood to refer to either hot-to-neutral or hot-to-ground faults. There many ways a short can occur such as nails and screws in a remodel project which may find a cable in the wall and short across its wires.
For instance; if the hot wire at a light fixture made contact with the metal of the fixture, which is grounded by a ground wire, sends a lot of current along this path can trip the breaker off. A "short" is understood to refer to either hot-to-neutral or hot-to-ground faults. There many ways a short can occur such as nails and screws in a remodel project which may find a cable in the wall and short across its wires.
Socket
Also referred to as a lamp holder. The part of a light fixture that receives the bulb or tube. People may 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.
Splice
An unanchored electrical connector joining two or more wires directly. Compare "Terminal".
Submain breaker
One of up to six (double) circuit breakers allowed till 1985 to be the means for disconnecting all power to a home's circuits. Since then a single "main breaker" has been the required means. This has provided a confusion, because submains were commonly labeled "Main". When a submain has trouble passing current through one of its six points of contact (at its 2 busbars, at its 2 wires, or at its 2 internal contacts), it will arc, overheat, possibly trip, and eventually fail to pass current any longer through that half. The result of this is that about half of the 120-volt circuits of the house (fed by that half) will be dead. If any 240-volt loads are fed from the submain breaker, they will not work and may enable the non-working 120-volt items to operate weakly and sporadically.
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".
Three-way
Although there is a type of light bulb and socket by this name, a three way system is one in which a light(s) is controllable from more than one location by two or more switches. The name comes from the usual number of terminals on or contact points within the switches involved.
Travelers
The pair of wires in a three-way switch system that are run (within the same cable) from one switch device to the next, attaching at each.
Voltage
The forcefulness with which electricity is ready to flow; also, the measurable relation of this force between two points ("volts"). Voltage can be present or fail to be present, and this is not identical with whether current is flowing or not. Current cannot flow if voltage is lacking, but even with voltage available, current will only flow if a continuous and conductive path is provided. Voltage is the "product" of current (amps) and resistance (ohms), but in practice current is the product, that is, the result, of a provided voltage acting on a given resistance.
Wattage
The rate of electric energy used by lights or appliances. It indicates the maximum watts a 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). 120 volts driving 15 amps through a resistance means 1800 watts is being used.
Wire
Wire is a flexible metal which can carry an electric current. Except when used as a grounding wire, it is coated with insulative material. In homes, wires that run to outlet and switch locations are mostly within cables; their sizes (gauges: "AWG") are (from smallest) 14, 12, 10, 8, 6, 4, etc., with larger wires at the meter and panel using a different numbering system. The function of each of wire type is not assured if they are not installed correctly or if they come apart at a connection or if they touch each other. A hot wire's connection can interrupt power along a circuit. If the neutral loses its continuity back to the main panel, the parts of the circuit that depend on that connection will no longer work.