BASIC ELECTRICAL TERMS Flashcards
— An electric current that reverses its direction
many times a second at regular intervals.
Alternating Current (AC)
— An instrument for measuring the flow of electrical current in amperes.
Anmeter
Ammeters are always connected in ___ with the circuit to be tested.
series
— The maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration.
Ampacity
A unit of measure for battery capacity.
Ampere-Hour (Ah)
Ampere-Hour (Ah) is obtained by multiplying ___ by ___during which current flows.
the current (in amperes) , the time (in hours)
A unit of measure for the intensity of an electric current flowing in a circuit.
Ampere
One ampere is equal to a current flow of ___ per second.
one coulomb
Measured in volt-ampers (VA)
Apparent Power
Apparent power is the product of the ___ and the ___.
rms voltage , rms current
The movable part of a generator or motor.
Armature
The pivoted points in generator
regulators are also called ___.
armatures
Armature is made up of ___ which rotate through a magnetic field to provide voltage or
force by electromagnetic induction.
conductors
The ability of a body to store an electrical charge.-
Capacitance
Capacitance is measured in ___ as the ratio of the electric charge of the object (Q, measured in coulombs) to the voltage across the object (V, measured in volts).
farads
— A device used to store an electric charge, consisting of one or
more pairs of conductors separated by an ___.
Capacitor : insulator
Commonly used for
filtering out voltage spikes.
Capacitor
— A closed path in which electrons from a voltage or current source flow.
Circuit
Circuits can be in ___ ,___, or ___
series : parallel : in any combination of the two
An automatic device for stopping the flow of current in an electric circuit.
Circuit Breaker
To restore service, the circuit breaker must be ___ after correcting the cause of the overload or failure.
reset(closed)
Circuit breakers are used in conjunction with
____ to protect circuits
from faults.
protective relays
Any material where electric current can flow freely.
Conductor
___ are the most common conductors.
Copper and aluminum wire
is an electrical discharge brought on by the ionization of a fluid such as air surrounding a conductor that is electrically charged.
Corona
Spontaneous corona discharges occur naturally in ___ unless care is taken to limit the electric field strength.
high-voltage systems
The flow of an electric charge through a conductor. An electric current can be compared to the flow of water in a pipe. Measured in amperes.
Current
The change in an alternating electrical sine wave from zero to a
positive peak to zero to a negative peak and back to zero. See Frequency.
Cycle
The average value of power or related quantity over a specified period of time.
Demand
A quantity measuring the ability of a substance to
store electrical energy in an electric field.
Dielectryc Constant
The maximum electric field that a pure material can withstand under ideal conditions without breaking down
Dielectryc Strength
— A semiconductor device with two terminals, typically allowing the flow of current in one direction only.
Diode
Diodes allow current to flow when
the anode is ____ to the cathode.
positive in relation
An electric current that flows in only one direction.
Direct Current
Any substance which, in solution, is dissociated into ions and is thus made capable of conducting an electrical current.
Electrolyte
___- water solution in a storage battery is an electrolyte.
The sulfuric acid
A difference in potential that tends to give
rise to an electric current. Measured in volts.
Electromotive Force
— A tiny particle which rotates around the nucleus of an atom. It has a negative charge of electricity.
Electron
The theory which explains the nature of electricity and the exchange of “free” electrons between atoms of a conductor. It is also used as one theory to explain direction of current flow in a circuit.
Electron Thoery
— A unit of measure for capacitance. One farad is equal to one coulomb per volt.
Farad
) a type of resonance in electric circuits which occurs when a circuit containing a nonlinear inductance is fed from a source that has series capacitance, and the circuit is subjected
to a disturbance such as opening of a switch.
Ferroresonance
Ferroresonance can cause __ and __
in an electrical power system and can pose a risk to transmission and distribution equipment and to operational personnel.
overvoltages : overcurrents
— The number of cycles per second. Measured in Hertz. If a current completes one cycle per second, then the frequency is 1 Hz; 60 cycles per second equals 60 Hz.
Frequency
A circuit interrupting device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.
Fuse
To restore service, the fuse must be replaced using a similar fuse with ___ and __ after correcting the cause of failure.
the same size : rating
A device which converts mechanical energy into electrical energy.
Generator
The reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
Ground
A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.
Ground Fault Circuit Interrupters
— A unit of measure for inductance. If the rate of change of current in a circuit is one ampere per second and the resulting electromotive force is one volt, then the inductance of the circuit is one henry.
Henry
A unit of measure for frequency. Replacing the earlier term of cycle per second (cps).
Hertz
The measure of the opposition that a circuit presents to a current when a voltage is applied.
Impedance
Impedance extends the concept of
resistance to AC circuits, and possesses both ___ and ___, unlike
resistance, which has only magnitude.
magnitude : phase
The property of a conductor by which a change in current flowing through it induces (creates) a voltage (electromotive force) in both the conductor itself (self-inductance) and in any nearby conductors (mutual inductance). Measured in henry (H).
Inductance
— A coil of wire wrapped around an iron core.
Inductor
The inductance is
directly proportional to the ___
number of turns in the coil
Any material where electric current does not flow freely. Insulative materials, such as glass, rubber, air, and many plastics have a relatively high resistance.
Insulator
An apparatus that converts direct current into alternating current.
Inverter
The product of power in kW and time in hours.
Equal to 1000 Watt-hours. For example, if a 100W light bulb is used for 4 hours, 0.4kWhs of energy will be used (100W x 1kW / 1000 Watts x 4 hours). Electrical energy is sold in units of kWh.
Kilowatt-hour (kWh)
A device used to measure electrical energy use.
Kilowatt (kW) — Equal to 1000 watts.
Kilowatt meter
Anything which consumes electrical energy, such as lights, transformers, heaters and electric motors.
Load
—The condition in which there is a sudden load loss in the system which causes the generating equipment to be over-frequency.
Load rejection
___ confirms that the system can withstand a sudden loss of load and return to normal operating conditions using its governor. ___ are normally used for these tests as part of the commissioning process for electrical power systems.
A load rejection test : Load banks
Occurs when changing current in one coil induces
voltage in a second coil.
Mutual Induction
— A unit of measure of resistance. One ohm is equivilant to the
resistance in a circuit transmitting a current of one ampere when subjected
to a potential difference of one volt.
Ohm(Ω)
The mathematical equation that explains the relationship between current, voltage, and resistance (V=IR).
Ohm’s Law
An instrument for measuring the resistance in ohms of an electrical circuit.
Ohmmeter
— occurs when a circuit is broken, such as by a broken wire or open switch, interrupting the flow of current through the circuit.
Open circuit
It is analogous to a closed valve in a water system.
Open Circuit
A circuit in which there are multiple paths for electricity to flow. Each load connected in a separate path receives the full circuit voltage, and the total circuit current is equal to the sum of the individual branch currents.
Parallel Circuit
Electric polarization in a substance (especially certain crystals) resulting from the application of mechanical stress (pressure).
Piezoelectricity
A collective term applied to the positive (+) and negative ( - ) ends of a magnet or electrical mechanism such as a coil or battery.
Polarity
The rate at which electrical energy is transferred by an electric circuit. Measured in Watts.
Power
The ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents power that does no useful work.
Power Factor
A relay device designed to trip a circuit breaker when a fault is detected.
Protective Relay
— The portion of electricity that establishes and sustains the electric and magnetic fields of AC equipment. Exists in an AC circuit when the current and voltage are not in phase. Measured in VARS.
Reactive Power
An electrical device that converts an alternating current into a direct one by allowing a current to flow through it in one direction only.
Rectifier
An electrical coil switch that uses a small current to control a much larger current
Relay
The resistance that a magnetic circuit offers to lines of force in a magnetic field.
Reluctance
The opposition to the passage of an electric current.
Resistance
Electrical ___ can be compared to the friction experienced by water
when flowing through a pipe. Measured in ohms.
resistance
A device usually made of wire or carbon which presents a resistance to current flow
Resistor
— The rotating part of an electrical machine such as a generator, motor, or alternator.
Rotor
Voltage which occurs in a coil when there is a change of current.
Self-Induction
A solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects. Devices made of semiconductors, notably silicon, are essential components of most electronic circuits.
Semiconductors
A circuit in which some of the circuit components
are connected in series and others are connected in parallel.
Series-Parallel Circuit
A circuit in which there is only one path for electricity to flow. All of the current in the circuit must flow through all of the loads.
Series Circuit
— The conductors and equipment used to deliver energy from the electrical supply system to the system being served.
Service
When one part of an electric circuit comes in contact with another part of the same circuit, diverting the flow of current from its desired path.
Short-Circuit
Electronic (integrated) circuits which utilize
semiconductor devices such as transistors, diodes and silicon controlled rectifiers.
Solid State Circuit
— A semiconductor device with three connections, capable of
amplification in addition to rectification.
Transistor
— Measured in Watts. The power manifested in tangible form such as electromagnetic radiation, acoustic waves, or mechanical phenomena. In a direct current (DC) circuit, or in an alternating current (AC) circuit whose impedance is a pure resistance, the voltage and current
are in phase.
True Power
— A unit of measure of reactive power.
VARS
___ may be considered as either the imaginary part of apparent power, or the power flowing into a reactive load, where voltage and current are specified in volts and amperes.
VARS
— A resistor that can be adjusted to different ranges of value.
Variable Resistor
A unit of measure of apparent power. It is the product of the rms voltage and the rms current.
Volt-Ampere
Volt-Ampere is the product of the ___ and the ___
rms voltage : rms current.
A unit measure of voltage. One volt is equal to the difference of potential that would drive one ampere of current against one ohm resistance.
Volt
— An electromotive force or “pressure” that causes electrons to flow and can be compared to water pressure which causes water to flow in a pipe. Measured in volts.
Voltage
— An instrument for measuring the force in volts of an electrical current. This is the difference of potential (voltage) between different points in an electrical circuit.
Voltmeter
___ have a high internal resistance are
connected across (parallel to) the points where voltage is to be measured.
Voltmeters
A unit of electrical energy equivalent to a power
consumption of one watt for one hour.
Watt-hour
— A unit of electrical power. One watt is equivalent to one joule per second, corresponding to the power in an electric circuit in which the potential difference is one volt and the current one ampere.
Watt
is an instrument for measuring the electric
power (or the supply rate of electrical energy) in watts of any given circuit.
Wattmeter
A graphical representation of electrical cycles which shows the amount of variation in amplitude over some period of time.
Waveform
