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Definitions of Household Electrical Terms

Glossary: Home Electrical Concepts and Components

What is electricity, what is a GFI, what is a ground fault, what is meant by a circuit? I think I am using electrical terms in this website according to their usual meanings by both electricians and homeowners. Still, there is quite a variety in how people use terms, and even more variety between countries. If nothing else, the following definitions will at least let you see what I mean by them. See my Electrical as a second language article. Here then is a glossary of home electrical terms related to troubleshooting:

What is 110??
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.
What is 220?
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. To understand the dual voltage available to homes (120/240), see Your system and Double circuit.
What is an Appliance?
A non-lighting item that, by its resistance, consumes electricity rather than just passing it on. So an appliance is not a fixture (for lighting) nor a device (for passing on). Examples: fax machine, garbage disposal, even a wired-in smoke alarm perhaps.
What is Arcing?
Current passing (through air) across a gap, that is, using the air itself like a wire.
What is an 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. See AFCI.
What is a 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.
What is a 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.
What is a 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.
What is a 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.
What is the 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.
What is 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, we tend to say that the power company is providing electricity that will flow "to" their neutral wire "from" hot wire. This directional talk can be misleading, since the actual electrons are moving back and forth sixty times per second. It is a way of speaking that is needed, however, in order to trace the paths of this kind of current in a wiring system. It is similar to how I may say that a highway goes "from" my hometown to the next town, even though the highway simply goes between them and doesn't really start at one or the other.
What is a 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.
What is a 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.
What is Electricity?
(That is, "tame" electricity, not The big stuff.) A force generated onto loops of conductive material, transferred through their electrons, and applied as useful energy at parts of these loops.
What is a Fixture?
Or "luminaire". A non-portable electrically-produced-light assembly. Distinguished from appliance or device.
What is a Fuse?
A device that interrupts current to its circuit by melting apart. It must then be replaced.
What is a Fusebox?
Like a panel, a usual main source of the circuits in a home. It contains fuses rather than breakers.
What is a Gang?
A combining of more than one device side-by-side, as, a "three-gang" switch box.
What is a GFI or GFCI?
A ground-fault interrupter. A device to prevent electrocution, which serves also as a receptacle or (less commonly) as a breaker. I consider the letters "GFCI" confusing because they stand for "ground-fault circuit interrupter" and the word "circuit" is vague and distracting. "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. Learn More about GFIs.
What is 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 so as to be 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, thereby also alerting us that a problem needs attention. If things were not grounded, people’s bodies would more often 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!).
What is a 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. Most shocks are an example.
What is "Hot"?
Or "live." (As an adjective:) Having electrical force (voltage) in relation to ground/earth, especially 120 volts. "Hot" is the termed 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.
What is Hotness?
Having voltage in relation to ground, especially 120 volts.
What is a 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.
What is a 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.
What is Line and Load?
These are 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 with that current.
What is a Neutral?
The wires of a circuit connected ultimately to the earth to receive flow "back" from a light or appliance. They are always supposed to be white. Contact with them should not normally shock you because they are normally connected to ground much better than you can be.
What is an Open?
(noun:) 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, but in regard to 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. I agree that the technical term "open," and its opposite "close" are a poor choice of words. They seem to come from the original use of "knife" switches; those had the physical appearance of an open door when they interrupted a circuit and a closed door when they let current through. But we are stuck with the terms.
What is an 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, however, we usually mean a receptacle. The following are not outlets: switch, breaker, junction box.
What is an 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".
What is a 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.
What is a Pigtail?
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. One illustration and another. Compare "Jumper". 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.
What is 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. See this explanation. ...Do not confuse phantom voltage 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.
What is a 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.
What is a Short?
A short circuit. I am including ground-faults here. A short is basically, 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 else providing 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. So it is called a "short" circuit. An example would be if the hot wire at a light fixture made contact with the metal of the fixture, which, being grounded by a ground wire, sends a lot of current through the circuit, tripping the breaker. Although this example is technically a ground-fault, in common parlance, "short" is understood to refer to either hot-to-neutral or hot-to-ground faults. There are at least as many ways a short can come about as there are outlets and lights on a circuit. Also a nail for hanging a picture or a screw in a remodel project will occasionally find a cable in the wall and short across its wires.
What is a 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.
What is a Splice?
An unanchored electrical connector joining two or more wires directly. Compare "Terminal".
What is a 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 busbars, at its wires, or at its 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. This is similar to what happens when a true main breaker has a similar problem, called a main hot open.
What is a Switch?
A device used to interrupt continuity and current to part of a circuit.
What is a 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".
What is Three-way?
Although there is a type of light bulb and socket by this name, here we mean a switching system 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. See How 3-way switches work, and Read more about 3-ways, including diagrams. For several ways that 3-way systems are wired, see my Tour of a Circuit [or frames version].
What are 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.
What is 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. The relation is: current cannot flow if voltage is lacking, but even with voltage available, current will only flow if a continuous and somewhat conductive path is provided. Mathematically 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.
What is 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). 120 volts driving 15 amps through a resistance means 1800 watts is being used.
What is a Wire?
A wire is bendable metal for carrying 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. To understand the function that different wires on a circuit play, see Hot or Neutral or Ground above, or see Background. The functioning of each of these wires is not assured if they were not installed correctly or if they come apart at a connection or if they touch each other unintentionally. And it is not just the hot wire’s connections that 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.

© 2006-2012 Larry Dimock

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