Electricity Flashcards
The science dealing with the physical phenomena arising from the existence and interaction of electric charges.
Electricity
The SI unit of electric charge, equal to the quantity of electricity transferred across a conductor by a current of one ampere in one second.
Coulumb or C
The energy per unit charge available for conversion from a chemical, mechanical, or other form of energy into electrical energy, or vice versa, in a conversion device such as a battery, generator or motor.
Electromotive Force or EMF
The voltage difference between two points that represents the work involved in the transfer of a unit charge from one point to the other.
Potential Difference
The work required to move a unit charge from a reference point to a designated point.
Potential
A group of two or more cells connected together to produce electric current.
Battery
A device for converting chemical into electric energy, usually consisting of a receptacle with electrodes in an electrolyte.
Cell, Electric Cell, Galvanic cell, or Voltaic Cell
A nonmetallic conducting medium in which current is carried by the movement of ions.
Electrolyte
A conductor through which a current enters or leaves a nonmetallic medium.
Electrode
The negative terminal of a primary cell or storage battery.
Anode
The positive terminal of a primary cell or storage battery.
Cathode
Potential difference or electromotive force expressed in volts, analogous to pressure in water flow.
Voltage
The SI unit of potential difference and electromotive force, defined as the difference of electric potential between two points of a conductor carrying a constant current of one ampere, when the power dissipated between the points is equal to one watt.
Volt or V
The complete path of an electric current, including the source of electric energy.
Circuit
An arrangement of components in an electric circuit in which the same current flows through each component in turn without branching.
Series
An arrangement of components in an electric circuit in which all positive terminals are connected to one conductor and all negative terminals are connected to a second conductor, the same voltage being applied to each component.
Parallel
The product of potential difference and current in a direct-current circuit. In an alternating current circuit, power is equal to the product of the effective voltage, the effective current, and the cosine of the phase angle between current and voltage.
Power
The rate of flow of electric charge in a circuit per unit time, measure in amperes.
Current
Before the nature of electricity was fully understood, it was assumed that a direct current flowed from a positive point to a negative one. This convention is still used even though electrons flow in the opposite direction, from negative to positive.
The opposition of a conductor to the flow of current, causing some of the electric energy to be transformed into heat and usually measured in ohms.
Resistance or R
The SI unit of electrical resistance, equal to the resistance of a conductor in which a potential difference of one volt produces a current of one ampere.
Ohm
The resistance per unit length of a substance with a unit cross-sectional area.
Resistivity or Specific Resistance
A measure of the ability of a substance to conduct electric current, equal to the reciprocal of the resistivity of the substance.
Conductivity or Specific Conductance
The law that for any circuit the electric current (I) is directly proportional to the voltage and inversely proportional to the resistance.
Ohm’s Law
I = V/R
The principle that the rate of production of heat by a direct current is directly proportional to the resistance of the circuit and to the square of the current.
Joule’s Law
The basic SI unit of electric current, equivalent to a flow of one coulumb per second or to the steady current produced by one volt applied across a resistance of one ohm.
Ampere or A
The strength of an electric current measured or expressed in amperes; analogous to the rate of water flow.
Amperage
The SI unit of power, equal to one joule per second or to the power represented by a current of one ampere flowing across a potential difference of one volt.
Watt or W
An amount of power, esp. the power required to operate an electrical device or appliance, expressed in watts.
Wattage
A unit of power, equal to 1000 watts.
Kilowatt or kW
A unit of energy, equal to the energy transferred or expended by one kilowatt in one hour; a common unit of electric power consumption.
kWh or kilowatt-hour
A machine that converts mechanical energy into electrical energy.
Generator
A generator for producing alternating current.
Alternator
A machine that converts electric power into mechanical energy.
Electric Motor
The main current carrying winding of a motor or generator in which electromotive force is induced.
Armature
A copper or carbon conductor serving to maintain electric contact between fixed and moving elements in a motor or generator.
Brush
A mass of iron or other ferrous material in an electromagnet, induction coil, or transformer, serving to concentrate and intensify the magnetic field resulting from a current in a surrounding coil.
Core
A conductor wound in a spiral form to introduce inductance into a circuit.
Coil
An electric current flowing in one direction only and having a magnitude that does not vary or varies only slightly.
Direct Current or DC
An electric current that reverses direction at regularly recurring intervals, having a magnitude that varies in a simusoidal manner.
Alternating Current or AC
A unit of electric measurement, equal to the product of one volt and one ampere, equivalent to one watt for direct-current systems and a unit of apparent power for alternating-current systems.
Volt-Ampere or VA
An electric device consisting of two or more windings wound on the same core, which employs the principle of mutual induction to convert variations of alternating current in a primary circuit into variations of voltage and current in a secondary circuit.
Transformer
A transformer having fewer turns in the primary winding than in the secondary, serving to transform low voltage to high voltage.
Step-up Transformer
A transformer having a greater number of turns in the primary winding than in the secondary, seving to transform high voltage to low voltage.
Step-down Transformer
An auxilliary power station where electrical current is converted, as from DC to AC, or where voltage is stepped up or down.
Substation
The supplying of utilities, such as water, gas and electricity, required or demanded by the public.
Service
Operated on, powered by, or transmitting high voltage.
High Voltage
The voltage supplied by a power line, measured at the point of use.
Line Voltage
Any of several conductors extending from a main power line or transformer to the service equipment of a building
Service Conductor
The overhead portion of service conductors extending from the nearest utility pole to a building.
Service Drop
The underground portion of service conductors extending from a main power line or transformer to a building.
Service Lateral
The decrease in voltage between two points on a power line, usually caused by resistance or leakage along the line.
Line Drop
The portion of a service conductor extending from a service drop or service lateral to the service equipment of a building.
Service Entrance Conductor.
A meter for measuring and recording the quantity of electric power consumed with respect to time.
Watt-hour Meter
A fire-rated room housing a transformer and auxiliary equipment for a large building, usually located on grade or below ground and ventilated directly to the outside air.
Transformer Vault
A room containing the service equipment for a building.
Switchgear room
The equipment necessary for controlling, metering, and protecting the electric power supply to a building, located near the entrance of the service conductors and usually consisting of a main disconnect switch and secondary switches, fuses and circuit breakers.
Service Equipment
A generator for providing emergency power during a power outage,
Standby Generator or Emergency Generator
An emergency system designed to provide power automatically and instantaneously upon failure of the normal power supply.
Uninteruptible power supply
One or a group of panels on which are mounted switches, overcurrent devices, metering instrucments, and buses for controlling and protecting a number of electric circuits.
Switchboard or Switchgear
Any of the conductors extending from the service equipment to various distribution points in a building.
Feeder
A freestanding enclosure housing a disconnect switch, a step-down transformer, and switchgear for a number of electric circuits.
Unit Substation
The fractional part of a period or cycle through which time has advanced, measured from a specified reference point and often expressed as an angle.
Phase
A conducting connection between an electric circuit or device and the earth or other point of zero potential.
Ground
Electrically connected to a source of voltage, or electrically charged so as to have a potential defferent from that of earth.
Live or Hot
Not electrically connected to a source of voltage.
Dead
Not electrically charged.
Neutral
A local failure in the insulation or continuity of a conductor, or in the functioning of an electrical system.
Fault
An abnormal, usually accidental condition of low resistance between two points in an electric circuit, resulting in a flow of excess current.
Short-Circuit
Of or pertaining to a circuit energized by an alternating current with one phase or with phases differing by 180d.
Single-Phase
Of or pertaining to a circuit energized by two alternating currents or voltages differing in phase by one quarter of a cycle or 90d.
Two-phase
Of or pertaining to a combination of three circuits energized by alternating currents or voltages differing in phase by one third of a cycle or 120d.
Three Phase
The main disconnect for the entire electrical system of a building, except for any emergency power systems.
Service Switch
A device containing a strip or wire of fusible metal that melts under the heat produced by excess current, thereby interrupting the circuit.
Fuse
Any of various metal alloys having a melting point below 300dF (70dC), used as solder and in various safety devices.
Fusible Metal or Fusible Alloy
A fuse housing a fusible link in a porcelain cup fitted with a threaded metal base.
Plug Fuse
A fuse having a one-time or renewable fusible link enclosed in an insulating fiber tube.
Cartridge Fuse
A cartridge fuse having a metal blade at each end for making contact with the fusible link within.
Knife-blade Fuse
A fuse that delays opening to allow a short-term overload to pass, as when starting a motor.
Time-Delay Fuse
A switch that automatically interrupts an electric circuit to prevent excess current from damaging apparatus in the circuit or from causing a fire. A circuit breaker may be reclosed and reused without replacement of any components.
Circuit Breaker
A circuit breaker that senses currents caused by ground faults and instantaneously shuts off power before damage or injury can occur.
Ground-Fault Interrupter or GFI
A board on which are mounted the switches, fuses and circuit breakers for controlling and protecting a number of similar branch circuits, installed in a cabinet and accessible from the front only.
Panel or Panel Board
A heavy conductor, usually in the form of a solid copper bar, used for collecting, carrying, and distributing large electric currents.
Bus or Busbar
Any conductor of an electrical system intentionally connected to a ground connection.
Grounded Conductor
A conductor, such a metal ground rod, ground plate, or cold-water pipe, firmly embedded in the earth to establish a ground connection.
Grounding Electrode
A conductor connecting electric equipment or a circuit to a ground connection.
Ground Wire or Grounding Conductor
Any of several conducting rods installed at the top of a structure and grounded to divert lightning away from the structure.
Lightning Rod
A device for protecting electric equipment from damage by lightning or other high-voltage currents, using spark gaps to carry the current to the ground without passing through the device.
Lightning Arrester
A space between two terminals or electrodes across which a discharge of electricity may pass at a prescribed voltage.
Spark Gap
The portion of an electrical system extending from the final overcurrent device protecting a circuit to the outlets served by the circuit.
Branch Circuit
A branch circuit that supplies current to a number of outlets for lighting and appliances.
General Purpose Circuit
A branch circuit that supplies current to one or more outlets specifically intended for appliances.
Appliance Circuit
A branch circuit that supplies current only to a single piece of electrical equipment.
Individual Circuit
A panel for distributing power to other panels or to motors and other heavy power-consuming loads.
Distribution Panel
Electric cable consisting of two or more insulated conductors protected by a flexible, helically wound metal wrapping.
Armored Cable or BX Cable
Electric cable consisting of a tubular copper sheath containing one or more conductors embedded in a highly compressed, insulating refractory mineral.
Mineral-insulated cable
Electric cable consisting of two or more insulated conductors enclosed in a nonmetallic, moisture-resistant, flame-retardant sheath.
Nonmetallic sheathed cable or Romex Cable
A cable for transmitting high-frequency telephone, digitalm or television signals, consisting of an insulated conducting tube enclosing an insulated conducting core.
Coaxial Cable
An electric cable enclosed within a metallic sheath in order to reduce the effects of external electric or magnetic fields.
Shielded Cable
A pliable metallic strand or a twisted or woven assembly of such strands, often insulated with a dielectric material and used as a conductor of electricity.
Wire
A material that is a poor conductor of electricity, used for separating or supporting conductors to prevent the undesired flow of current.
Insulator
The minimum applied voltage at which a given insulator breaks down and permits current to pass.
Breakdown Voltage
An enclosure for housing and protecting electric wires or cables that are joined together in connecting or branching electric circuits.
Junction Box
A panel in a casing or box that can readily be removed, as by punching, hammering, or cutting, to provide an opening into the interior.
Knockout
A rubber or plastic washer inserted in a hole in a metal part to prevent grounding of awire passing through the hole.
Grommet
An insulating and protective lining for one or more conductors passing through a hole.
Bushing
Heavy-walled, tubular steel conduit joined by screwing directly into a threaded hub with locnuts and bushings
Rigid Metal Conduit
Thin-walled, tubular steel conduit joined by compression or setscrew couplings.
Electrical metallic tubing or EMT
A flexible, helically wound metal conduit, used for connections to motors or other vibrating equipment.
Flexible Metal Conduit or Greenfield Conduit
An enclosed raceway for housing conductors or cables.
Duct
A rigid metal housing for a group of buses insulated from each other and the enclosure.
Bus Duct or Busway
A raceway designed for exposed installation in dry, nonhazardous, noncorrosive locations.
Surface Raceway
A surface-mounted raceway designed to house the electrical wires for a circuit and a series of receptacles.
Multi-outlet assembly
A raceway suitable for installation under a floor, often used in office buildings to allow for the flexible placement of power, signal, and telephone outlets.
Underfloor Raceway
An open metal framework for supporting insulated electrical conductors.
Cable Tray
A switch in which the interruption of a circuit occurs in air.
Air Switch
A form of air switch in which a hinged copper blade is placed between two contact clips.
Knife Switch
A float switch controlled by a conductor floating in a liquid.
Float Switch
An especially quiet switch that opens and closes an electric circuit by shifting a sealed glass tube of mercury so as to uncover or cover the contacts.
Mercury Switch
A switch operated only by inserting a key.
key switch
A protective plate surrounding an electric outlet or light switch,
Faceplate
A switch in which a lever or know, moving through a small arc, causes the contacts to open or close an electric circuit.
Toggle Switch
A rheostat or similar device for regulating the intensity of an electric light without appreciably affecting spatial distribution.
Dimmer or Dimmer Switch
A resistor for regulating a current by means of variable resistances.
Rheostat
A single-pole, double-throw switch used in conjunction with another to control lights from two locations.
Three-way Switch
A switch used in conjunction with two three-way switches to control lights from three locations.
Four-way Switch
An obsolete wiring system consisting of single, insulated conductors secured to and supported on porcelain knobs and tubes.
Knob-and-tube wiring
A point on a wiring system at which current is taken to supply an electric device or apparatus.
Outlet
A junction box designed to facilitate connecting an electric device or receptacle to a wiring system.
Outlet Box
An outlet usually mounted on a wall and housing one or more receptacles for portable lamps or appliances.
Convenience Outlet
A female fitting connected to a power supply and equipped to receive a plug.
Receptacle or Socket
A flexible, insulated conductr for electrically connecting an apparatus to another or to a circuit.
Lead
A small, flexbile, insulated cable fitted with a plug to connect a portable lamp or appliance to a receptacle.
Cord
A plastic connector containing a threaded metal fitting for screwing onto the interwined ends of two or more conductors.
Wire nut
A male fitting for making an electrical connection to a circuit by insertion in a receptacle.
Plug
A plug having a blade for a ground connection.
Grounding Plug
Designed so that a plug and receptacle can fit together in only one way.
Polarized
