BASIC ELECTRICAL TERMS Flashcards
(104 cards)
1
Q
— An electric current that reverses its direction
many times a second at regular intervals.
A
Alternating Current (AC)
2
Q
— An instrument for measuring the flow of electrical current in amperes.
A
Anmeter
3
Q
Ammeters are always connected in ___ with the circuit to be tested.
A
series
4
Q
— The maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration.
A
Ampacity
5
Q
A unit of measure for battery capacity.
A
Ampere-Hour (Ah)
6
Q
Ampere-Hour (Ah) is obtained by multiplying ___ by ___during which current flows.
A
the current (in amperes) , the time (in hours)
7
Q
A unit of measure for the intensity of an electric current flowing in a circuit.
A
Ampere
8
Q
One ampere is equal to a current flow of ___ per second.
A
one coulomb
9
Q
Measured in volt-ampers (VA)
A
Apparent Power
10
Q
Apparent power is the product of the ___ and the ___.
A
rms voltage , rms current
11
Q
The movable part of a generator or motor.
A
Armature
12
Q
The pivoted points in generator
regulators are also called ___.
A
armatures
13
Q
Armature is made up of ___ which rotate through a magnetic field to provide voltage or
force by electromagnetic induction.
A
conductors
14
Q
The ability of a body to store an electrical charge.-
A
Capacitance
15
Q
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).
A
farads
16
Q
— A device used to store an electric charge, consisting of one or
more pairs of conductors separated by an ___.
A
Capacitor : insulator
17
Q
Commonly used for
filtering out voltage spikes.
A
Capacitor
18
Q
— A closed path in which electrons from a voltage or current source flow.
A
Circuit
19
Q
Circuits can be in ___ ,___, or ___
A
series : parallel : in any combination of the two
20
Q
An automatic device for stopping the flow of current in an electric circuit.
A
Circuit Breaker
21
Q
To restore service, the circuit breaker must be ___ after correcting the cause of the overload or failure.
A
reset(closed)
22
Q
Circuit breakers are used in conjunction with
____ to protect circuits
from faults.
A
protective relays
23
Q
Any material where electric current can flow freely.
A
Conductor
24
Q
___ are the most common conductors.
A
Copper and aluminum wire
25
is an electrical discharge brought on by the ionization of a fluid such as air surrounding a conductor that is electrically charged.
Corona
26
Spontaneous corona discharges occur naturally in ___ unless care is taken to limit the electric field strength.
high-voltage systems
27
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
28
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
29
The average value of power or related quantity over a specified period of time.
Demand
30
A quantity measuring the ability of a substance to
store electrical energy in an electric field.
Dielectryc Constant
31
The maximum electric field that a pure material can withstand under ideal conditions without breaking down
Dielectryc Strength
32
— A semiconductor device with two terminals, typically allowing the flow of current in one direction only.
Diode
33
Diodes allow current to flow when
the anode is ____ to the cathode.
positive in relation
34
An electric current that flows in only one direction.
Direct Current
35
Any substance which, in solution, is dissociated into ions and is thus made capable of conducting an electrical current.
Electrolyte
36
___- water solution in a storage battery is an electrolyte.
The sulfuric acid
37
A difference in potential that tends to give
rise to an electric current. Measured in volts.
Electromotive Force
38
— A tiny particle which rotates around the nucleus of an atom. It has a negative charge of electricity.
Electron
39
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
40
— A unit of measure for capacitance. One farad is equal to one coulomb per volt.
Farad
41
) 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
42
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
43
— 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
44
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
45
To restore service, the fuse must be replaced using a similar fuse with ___ and __ after correcting the cause of failure.
the same size : rating
46
A device which converts mechanical energy into electrical energy.
Generator
47
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
48
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
49
— 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
50
A unit of measure for frequency. Replacing the earlier term of cycle per second (cps).
Hertz
51
The measure of the opposition that a circuit presents to a current when a voltage is applied.
Impedance
52
Impedance extends the concept of
resistance to AC circuits, and possesses both ___ and ___, unlike
resistance, which has only magnitude.
magnitude : phase
53
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
54
— A coil of wire wrapped around an iron core.
Inductor
55
The inductance is
directly proportional to the ___
number of turns in the coil
56
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
57
An apparatus that converts direct current into alternating current.
Inverter
58
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)
59
A device used to measure electrical energy use.
Kilowatt (kW) — Equal to 1000 watts.
Kilowatt meter
60
Anything which consumes electrical energy, such as lights, transformers, heaters and electric motors.
Load
61
—The condition in which there is a sudden load loss in the system which causes the generating equipment to be over-frequency.
Load rejection
62
___ 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
63
Occurs when changing current in one coil induces
voltage in a second coil.
Mutual Induction
64
— 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)
65
The mathematical equation that explains the relationship between current, voltage, and resistance (V=IR).
Ohm's Law
66
An instrument for measuring the resistance in ohms of an electrical circuit.
Ohmmeter
67
— 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
68
It is analogous to a closed valve in a water system.
Open Circuit
69
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
70
Electric polarization in a substance (especially certain crystals) resulting from the application of mechanical stress (pressure).
Piezoelectricity
71
A collective term applied to the positive (+) and negative ( - ) ends of a magnet or electrical mechanism such as a coil or battery.
Polarity
72
The rate at which electrical energy is transferred by an electric circuit. Measured in Watts.
Power
73
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
74
A relay device designed to trip a circuit breaker when a fault is detected.
Protective Relay
75
— 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
76
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
77
An electrical coil switch that uses a small current to control a much larger current
Relay
78
The resistance that a magnetic circuit offers to lines of force in a magnetic field.
Reluctance
79
The opposition to the passage of an electric current.
Resistance
80
Electrical ___ can be compared to the friction experienced by water
when flowing through a pipe. Measured in ohms.
resistance
81
A device usually made of wire or carbon which presents a resistance to current flow
Resistor
82
— The rotating part of an electrical machine such as a generator, motor, or alternator.
Rotor
83
Voltage which occurs in a coil when there is a change of current.
Self-Induction
84
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
85
A circuit in which some of the circuit components
are connected in series and others are connected in parallel.
Series-Parallel Circuit
86
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
87
— The conductors and equipment used to deliver energy from the electrical supply system to the system being served.
Service
88
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
89
Electronic (integrated) circuits which utilize
semiconductor devices such as transistors, diodes and silicon controlled rectifiers.
Solid State Circuit
90
— A semiconductor device with three connections, capable of
amplification in addition to rectification.
Transistor
91
— 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
92
— A unit of measure of reactive power.
VARS
93
___ 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
94
— A resistor that can be adjusted to different ranges of value.
Variable Resistor
95
A unit of measure of apparent power. It is the product of the rms voltage and the rms current.
Volt-Ampere
96
Volt-Ampere is the product of the ___ and the ___
rms voltage : rms current.
97
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
98
— 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
99
— 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
100
___ have a high internal resistance are
connected across (parallel to) the points where voltage is to be measured.
Voltmeters
101
A unit of electrical energy equivalent to a power
consumption of one watt for one hour.
Watt-hour
102
— 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
103
is an instrument for measuring the electric
power (or the supply rate of electrical energy) in watts of any given circuit.
Wattmeter
104
A graphical representation of electrical cycles which shows the amount of variation in amplitude over some period of time.
Waveform
