DK Ching VD - Electricity

electricity

the science of dealing with the physical phenomena arising from the existence and interaction of electric charges

electric charge

the intrinsic property of matter giving rise to all electric phenomena

coulomb

SI unit of electric charge

electromotive force

the energy per unit charge available for conversion from a chemical, mechanical, or other form of energy into electrical energy

potential difference

the voltage difference between two points that represents the work involved in the transfer of a unit charge from one point to the other

electrode

a conductor through which a current enters or leaves a nonmetallic medium

anode

the negative terminal of a primary cell or storage

cathode

the positive terminal of a primary cell or storage battery

voltage

potential difference or electromotive force expressed in volts; analogous to pressure in water flow

volt

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

circuit

the complete path of an electric current, including the source of electric energy

series

an arrangement of components in an electric circuit in which the same current flows through each component in turn without branching

parallel

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

power

the product of potential difference and current in a direct-current circuit

watt

the SI unit of power, equal to one joule per second

wattage

an amount of power

current

the rate of flow of electric charge in a circuit per unit time, measured in amperes

ampere

the basic SI unit of electric current

amperage

the strength of an electric current measured or expressed in amperes, analogous to the rate of water flow

resistance

the opposition of a conductor to the flow of current

ohm

the SI unit of electrical resistance

ohm's law

the law that for any circuit the electric current (I) is directly proportional to the voltage and inversely proportional to the resistance

joule's law

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

generator

a machine that converts mechanical energy to electrical energy

alternator

a generator for producing alternating current

electric motor

a machine that converts electric power into mechanical energy

armature

the main current-carrying winding of a motor or generator in which electromotive force is induced

brush

a copper or carbon conductor serving to maintain electric contact between fixed and moving elements in a motor or generator

direct current

an electric current flowing in one direction only and having a magnitude that does not vary or varies only slightly

alternating current

an electric current that reverses direction at regularly recurring intervals, having a magnitude that varies in a sinusoidal manner

core

a mass of iron or other ferrous material in an electromagnet, induction coil, or transformer

coil

a conductor wound in a spiral form to introduce inductance into a circuit

transformer

an electric device consisting of two or more windings wound on the same core

step-up transformer

a transformer having fewer turns in the primary winding than in the secondary, serving to transform low voltage to high voltage

step-down transformer

a transformer having a greater number of turns in the primary winding than in the secondary, serving to transform high voltage to low voltage

line voltage

the voltage supplied by a power line

service conductor

any of several conductors extending from a main power line or transformer to the service equipment of a building

service drop

the overhead portion of service conductors extending from the nearest utility pole to a building

service lateral

the underground portion of service conductors extending from a main power line or transformer to a building

line drop

the decrease in voltage between two points on a power line, usually caused by resistance or leakage along the line

service entrance conductor

the portion of a service conductor extending from a service drop or service lateral to the service equipment of a building

watt-hour meter

a meter for measuring and recording the quantity of electric power consumed with respect to time

transformer vault

a fire-rated room housing a transformer and auxiliary equipment for a large building

standby generator

a generator for providing emergency power during a power outage

uninterruptible power supply

an emergency system designed to provide power automatically and instantaneously upon failure of the normal power supply

switchgear room

a room containing the service equipment for a building

service equipment

the equipment necessary for controlling, metering, and protecting the electric power supply to a building

switchboard

one or a group of panels on which are mounted switches, overcurrent devices, metering instruments, and buses for controlling and protecting a number of electric circuits

feeder

any of the conductors extending from the service equipment to various distribution points in a building

unit substation

a freestanding enclosure housing a disconnect switch, a step-down transformer, and switchgear for a number of electric circuits

ground

a conducting connection between an electric circuit or device and the earth or other point of zero potential

single-phase

of or pertaining to a circuit energized by an alternating current with one phase or with phases differing by 180 degrees

two-phase

of or pertaining to a circuit energized by two alternating current or voltages differing in phase by one quarter of a cycle or 90 degrees

three-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 120 degrees

live

electrically connected to a source of voltage

dead

not electrically connected to a source of voltage

neutral

not electrically charged

fault

a local failure in the insulation or continuity of a conductor, or in the functioning of an electric system

short circuit

an abnormal, usually accidental condition of low resistance between two points in an electric circuit, resulting in a flow of excess current

fuse

a device containing a strip or wire of fusible metal that melts under the heat produced by excess current, thereby interrupting the circuit

plug fuse

a fuse housing a fusible link in a porcelain cup fitted with a threaded metal base

cartridge fuse

a fuse having a one-time or renewable fusible link enclosed in an insulating fiber tube

knife-blade fuse

a cartridge fuse having a metal blade at each end for making contact with the fusible link within

time-delay fuse

a fuse that delays opening to allow a short-term overload to pass, as when starting a motor

service switch

the main disconnect for the entire electrical system of a building, except for any emergency power systems

panel

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

bus

a heavy conductor, usually in the form of a solid copper bar, used for collecting, carrying, and distributing large electric currents

grounded conductor

any conductor of an electrical system intentionally connected to a ground connection

grounding electrode

a conductor, such as a metal ground rod, ground plate, or cold-water pipe, firmly embedded in the earth to establish a ground connection

ground wire

a conductor connecting electric equipment or a circuit to a ground connection

circuit breaker

a switch that automatically interrupts an electric circuit to prevent excess current from damaging apparatus in the circuit or from causing a fire

ground-fault interrupter

a circuit breaker that senses currents caused by ground faults and instantaneously shuts off power before damage or injury can occur

load

the power delivered by a generator or transformer, or the power consumed by an appliance or device

connected load

the total load on an electrical system or circuit if all connected apparatus and equipment are energized simultaneously

maximum demand

the greatest load delivered to an electrical system or circuit over a specified interval of time

demand factor

the ratio of the maximum demand to the connected load of an electrical system

diversity factor

the ratio of the sum of the maximum demands on the various parts of an electrical system to the maximum demand on the whole

load factor

the ratio of the average load on an electrical system over a specific period of time to the peak load occurring in that period

lightning rod

any of several conducting rods installed at the top of a structure and grounded to divert lightning away from the structure

lightning arrester

a device for protecting electric equipment from damage by lightning or other high-voltage currents

spark gap

a space between two terminals or electrodes, across which a discharge of electricity may pass at a prescribed voltage

branch circuit

the portion of an electrical system extending from the final overcurrent device protecting a circuit to the outlets served by the circuit

distribution panel

a panel for distribution power to other panels or to motors and other heavy power consuming loads

general purpose circuit

a branch circuit that supplies current to a number of outlets for lighting and appliances

appliance circuit

a branch circuit that supplies current to one or more outlets specifically intended for appliances

individual circuit

a branch circuit that supplies current only to a single piece of electrical equipment

cable

a single insulated conductor or a bound or sheathed combination of conductors insulated from one another

armored cable / BX

electric cable consisting of two or more insulated conductors protected by a flexible, helically wound metal wrapping

mineral-insulated cable

electric cable consisting of a tubular copper sheath containing one or more conductors embedded in a highly compressed, insulating refractory mineral

nonmetallic sheathed cable / romex

electric cable consisting of two or more insulated conductors enclosed in a nonmetallic, moisture-resistant, flame-retardant sheath

coaxial cable

a cable for transmitting high-frequency telephone, digital, or television signals, consisting of an insulated conducting tube enclosing an insulated conducting core

shielded cable

an electric cable enclosed within a metallic sheath in order to reduce the effects of external electric or magnetic fields

wire

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

conductor

a substance, body, or device that conducts heat, sound, or electricity

insulator

a material that is a poor conductor of electricity, used for separating or supporting conductors to prevent the undesired flow of current

breakdown voltage

the minimum applied voltage at which a given insulator breaks down and permits current to pass

dielectric

a nonconducting substance

conduit

a tube, pipe, or duct for enclosing and protecting electric wires or cable

rigid metal conduit

heavy-walled, tubular steel conduit joined by screwing directly into a threaded hub with locknuts and bushing

electrical metallic tubing

thin-walled, tubular steel conduit joined by compression or setscrew couplings