Glossary  of  Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link.

- A -

Alternating Current (AC)
An electrical current that periodically changes in magnitude and in the direction of current flow. Household current in the United States changes direction 120 times per second, or 60 complete cycles per second.

Ampere (amp)
A measure of electrical current flow. One ampere flows in a circuit that has one ohm of resistance when one volt is applied ({Current = Voltage/Resistance} or {Amps = volts/ohms} or {I = E/R *}). Also, power is a measure of the current flow times the applied voltage; for example, a 150 Watt lamp draws about 1.25 Amperes (Current = 150W / 120V). * See also, electrical "symbols".
Arc Fault Circuit Interrupter, a type of circuit interrupter designed to protect against certain hazardous arcing problems, those that generally occur below 75 amps. Multiple proposals are under consideration by the NFPA; and, a consolidated standard is expected to be announced sometime in 1999 as a supplement to the National Electrical Code (NEC). At present it is not required that an AFCI (or the present GFCI) include basic circuit overload detection and protection.
A luminous discharge of electrical current in air. A band of sparks or incandescent light formed when an electrical discharge is conducted from one electrode or conducting surface to another. Two types exist in residential and commercial buildings:
Parallel Arcs
Series Arcs
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- B -

Bi-metal (bi-metallic)
A component consisting of two metals having different coefficients of thermal expansion (i.e., they expand differently when heated). They are joined together such that when heat is applied, the combined strip will bend. Used in conventional circuit breakers to measure current flow by passing the current through the bi-metal strip, thereby heating it; and, because the bi-metal strip heats slowly it provides a necessary delay in the breaker's trip time.
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- C -

A thin piece of silicon, sometimes smaller than the size of a fingernail, that contains thousands (often hundreds of thousands) of transistors. They are all connected in such a fashion as to form a computer, or mega-bit memory, or other devices that are used in the world of electronics.
The path that allows electrical current to flow from one terminal of a voltage source to the other terminal.
There are two types: Open Circuit (no current can flow) , Closed Circuit (allows current flow based on the voltage and resistance of the circuit: I=E/R, See also, electrical symbols)
Circuit Breaker
An automatic switch that stops the flow of electrical current when it exceeds a certain value and time. This limit is designed to protect the circuit wiring from overheating due to excessive load currents. A delay in response is included to prevent nuisance tripping due to large surge currents that occur when starting many types of appliances. Some motors, protected by a 20 amp circuit breaker, require more than 100 amps of startup current.
Closed Circuit
A completed path that allows electrical current to flow from one terminal of a voltage source to the other terminal. The current is limited by the voltage and resistance: I=E/R.
A substance, such as copper or aluminum, through which electrical current flows with relative ease.
Consumer Product Safety Commission. An independent Federal regulatory agency dedicated to reducing the risk of injury or death from consumer products.
The flow of electrons through a circuit. Current is measured in amperes, where amps = voltage / resistance (I=E/R, see symbols).
One complete period of an alternating current flow from positive to negative (direction) and back again. Household current in the United States is 60 cycles per second (referred to as 60 Hertz). Some other countries use 50 Hertz (cycle) line frequency. Most aviation electrical products use 400 Hertz to reduce the weight of transformers and related components.
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- D -

Direct Current (DC)
Electrical current that always flows in the same direction. A car battery is an example of Direct Current. It varies in magnitude (how much current is used e.g. radio versus the starter) but always travels in the same direction. (See also: 'Alternating Current')
Digitally Enhanced (DE)
Digital: to improve data processing precision using computer states of "1's" & "0's". A Digitally Enhanced circuit breaker is one that employs a digital processor (computer chip) to extract and distinguish hazardous conditions from normal operating current loads. Using digital enhancement, Zlan has been able to demonstrate up to 10,000% improvement over the standard thermal/magnetic circuit breaker.
DE Breaker
A conventional circuit breaker that has been "enhanced" (augmented, improved ...) using digital technology. The original current overload mechanism is retained as a safety feature.
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- E -

A form of energy produced by the flow of electrons through materials and ionized gases under the influence of an electromotive force.
Electromotive force
An electrical force applied to a circuit, measured in volts. Electric potential, or potential difference.
Negatively charged particles that form the outer shell of an atom. The movement of 'free' electrons through a conductor is called the flow of electrical current and is measured in amps.
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- F -

A measure of the number of cycles per second of an alternating electrical current. Frequency is stated in Hertz; e.g., 60 Hz refers to 60 cycles per second alternating current.
The fuse is the earliest form of circuit protection device ever used. In fact, there are many applications where the fuse is still the preferred type of circuit breaker. It consists of a metal strip designed to burn-up (fuse) when the current exceeds its design rating. Its advantage is in the automatic delay inherent in the heating of metal; i.e., it has an I2t characteristic, where the delay time varies inversely with the square of the current. This delay is necessary to allow motors and some other appliances to start, even though their starting surge currents may momentarily exceed the fuse rating by 500%.
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- G -

A standard for indicating linear dimensions such as the diameter of wire. It is actually an inverse logarithmic function, e.g., #10 gauge wire is twice the size of #16 gauge wire. Since the cross sectional area of wire determines its ability to carry current, a #10 wire can carry 4 times the current of the #16 wire gauge.
Ground Fault Circuit Interrupter, a type of circuit interrupter (breaker) that protects against hazardous electrical shock. They are now required to be used in locations where people are most susceptible to being shocked: the bathroom, kitchen and garage. They are not designed to protect against arcs or circuit overloads.
An electrical voltage reference point, normally connected to earth ground.
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- H -

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- I -

Ionized gases
Atoms or molecules that have acquired a net electric charge by gaining or losing electrons from a neutral configuration. Usually associated with neon lights, florescent lamps and the arc of an arc welder. Ionized gases are considered to be a conductor of electricity.
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- J -

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- K -

Kilowatt (kW)
A unit of electrical power, equal to 1000 watts.
Kilowatt-Hour (kWh)
The amount of energy delivered when 1000 watts is used for one hour. The consumer typically pays a few cents per kWh for this energy.
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- L -

Load is a generic name that may be used in place of "appliance or heater or light or other objects" that draw electrical current to perform a job, hopefully a useful job. An "overload" is a load that draws more current than the circuit breaker, wiring, and its connections, are designed to support.
Load center, Load panel
Load center (panel) is the common name used in the electrician's world to describe the electrical junction box containing all the circuit breakers for the home or business.
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- M -

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- N -

National Electrical Code. A document published and recommended by the National Fire Protection Association "for use in law and for regulatory purposes in the interest of life and property protection". The latest NEC edition is "NFPA 70-1996", the next edition is due in 1999.
National Electrical Manufacturers Association. A private organization that makes recommendations to National Electrical Code Committee of the NFPA, and its Code-Making Panels, on proposed revisions and updates to the National Electrical Code.
National Fire Protection Association. The mission of this international nonprofit organization is protecting people, property, and the environment from the effects of fire and related hazards through education, codes and standards, research, and technical advisory services. The NFPA has acted as sponsor of the National Electrical Code since 1911.
Nuisance tripping
A nuisance circuit breaker trip is when the circuit breaker trips because it mistakes a normal operating condition for a hazardous condition, such as high motor startup currents. A 20 amp circuit breaker must withstand more than 100 amps of motor startup current.
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- O -

The unit of electrical resistance. A circuit component having a resistance of one ohm will allow one amp to flow through it when one volt is applied to its terminals ({Resistance = Voltage / Current} or {Ohms = Volts / Amps} or {R=E/I}). Ohm Meter -- An instrument for measuring electrical resistance in ohms.
Open Circuit
An electrical circuit that has a break in its path, such as an ON/OFF switch, so that current is unable to flow.
An appliance or circuit fault that causes too much electrical current to flow, thus exceeding the design limit of the wiring, connections and circuit breaker's rating.
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- P -

Parallel Arcs
Are the result of a short circuit across the power line; i.e., line to neutral or line to ground. These arcs are very large and dangerous in that the current is limited only by the wiring resistance involved and can generate very hot sparks; e.g., welder's arcs. They may occur within: the building wiring, terminal boxes, wall receptacles, external cords, or within appliances themselves.
Measured in watts, is the amount of energy expended per unit time. Power is also a measure of the current flow times the applied voltage (e.g., a 1200 Watt hair dryer is equal to 10 Amps * 120 Volts: P=I*E).
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- Q -

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- R -

In electrical and electronic circuits, a characteristic of materials that opposes the flow of current, measured in ohms. It results in loss of energy, which is dissipated as heat. (R=E/I, see symbols)
A device used in a circuit to control the current flow. Current flow is equal to the applied Voltage divided by the Resistance of a circuit (Amperes = Volts / Ohms)
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- S -

Series Arcs
Series arcing is arcing current which is limited by the load or appliance current. If a toaster uses 12 amps of current, then series arcing in the wiring or connections can only cause a maximum arc of 12 amps. Hence, the arcing current is limited by the appliance current. Should arcing occur at a loose connection, all current passing through that connection makes up the arcing current; i.e. a 12 amp toaster and a 5 amp light could produce a 17 amp series arc. A Repeated series arcs will cause localized heating which could lead to the more serious Parallel Arc.
Short-Circuit Current
The maximum current obtained when shorting the hot wire to the neutral or ground wire. This is often referred to as Parallel Arcing.
Symbols, Electrical
Electrical formulas do not always use symbols representative of the units of measure; i.e., E is the common symbol for voltage (in Volts), I is used for current (in Amperes), R is used for resistance (in Ohms), and P is used for power (in Watts). They are related algebraically by: E=I*R, I=E/R, R=E/I, P=I*E, and by substitution, P=I2R or P=E2/R.
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- T -

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- U -

Underwriters Laboratories. The leading certification organization in the U.S. UL has been evaluating products since 1894.
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- V -

Voltage (volt)
"Volt" is the unit of electrical force that causes current to flow in a closed circuit. The voltage available in house wiring is approximately 120 volts for appliances requiring moderate amounts of power and 240 volts for those requiring large amounts of power, such as, air conditioners. (E=I*R, see symbols)
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- W -

Amount of electrical power expressed in watts required to operate a given appliance or device. It is the applied voltage times the current flowing through the device. (P=I*E, see symbols)
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- X -

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- Y -

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- Z -

Zlan, Ltd.
Zlan is a research and development firm dedicated to reducing the risk of electrical fires by enhancing conventional circuit breakers with new electronic technology. (Zlan is pronounced by using a slight accent on the Z as in, Zee'-Lan or Zee'-Lun)
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