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Flashcards in Electricity Information Deck (117):
1

Direct Current

-Current that flows in only one direction.
-battery

2

Current
(Amps) (I)

-The flow of electrons through a conductor.
-Flow

3

Voltage
(E)

-The driving force that makes electrons flow.
-Pressure

4

Resistance
(R)

-The electrical quantity that opposes electron flow in a circuit.
-Ohm

5

Series Circuit

-Current has only one path.

6

Parallel Circuit

-Current has more than one path.

7

Amp

-Measure of electric current flow.

8

Watt

-Measure of real electric power.
-The electrical power required to do work at the rate of 1 joule per second.

9

US Frequency

-60 cycles per second (Hz).

10

Inverter

-Turns DC into AC.

11

Rectifier

-An electrical device that converts AC to DC.

12

Recloser

-A circuit breaker equipped with a mechanism that can automatically close the breaker after it has been opened due to fault.
-Automatically restores power to a line after a momentary fault.

13

Protective Relay

-Designed to calculate operating conditions on an electrical circuit and trip circuit breakers when a fault is detected.
-Have well established, selectable, time/current(or other operating parameter) operating characteristics.

14

Potential Transformer (PT)

-Used for metering and protection in high voltage circuits, step voltage up or down.
-Instrument transformer used to supply voltage to protective relays for metering.

15

Current Transformer (CT)

-Primary functions are measuring current, stepping current up or down (usually down)and relaying current to protective system controllers.
-Produces a secondary current proportional to the primary current.

16

Relay

-Electrically operated switch.
-Use an electromagnet to mechanically operate a switch.
-An electrical magnetic switch employing an armature to open or close contacts.

17

Electrical Contact

-An electrical circuit component found in electrical switches, relays, and breakers.
-Composed of 2 pieces of electrically conductive metal that pass electrical current or insulate when the gap between them is open or closed.

18

3 Things needed to make electricity?

1. Magnetic Field
2. Relative Motion
3. Conductor
-If connected to a closed circuit electricity will flow.

19

How does electricity compare to water?

-Voltage = Pressure
-Amps = Flow Rate
-Ohms = Resistance

20

Ohm's Law

E
I R
E = Voltage
I = Amps
R = Resistance

21

Purpose of Grounding

-To reduce the risk of electrical shock.
-To safeguard against fire.
-To protect electrical equipment from damage.

22

Generator Theory of Operation

-A magnet rotates through a magnetic field which cuts the lines of flux. When the lines are cut voltage is induced into the stator windings. If connected to a closed circuit electricity will flow.

23

Generator

-Converts mechanical energy into electrical energy.

24

Turns Ratio

-The ratio of the number of turns on the primary coil of an electrical transformer to the number of turns on the secondary, or vice versa.

25

Mutual Inductance

-The principle that a change of current in one circuit can induce electromotive force in a neighboring circuit.

26

Induction

-Process by which an electrical conductor becomes electrified when near a charged body.
-Magnetizable body becomes magnetized when in a magnetic field

27

Electro Magnetic Induction

-Production of an electromotive force across a conductor when it is exposed to a varying magnetic field.

28

Electromotive Force

-Voltage developed by any source of electrical energy such as a battery.

29

Electromagnet

-A soft metal core made into a magnet by the passage of electric current through a coil surrounding it.

30

RTD

-Resistance Temperature Detector

31

Transistor

-A semiconductor device used to amplify and switch electronic signals and electrical power.

32

Semi Conductor

-Solid substance that has conductivity between that of an insulator and that of most metals.
-Silicon

33

Connecting Batteries in Parallel

-Two or more batteries whose terminals are connected positive-to-positive and negative-negative, with the load connected across the positive and negative leads.
-The available current is equal to the sum of the individual battery current ratings, and the voltage rating of one battery.
-Only batteries of equal voltage may be connected in this manner.
-Double capacity(Amp hours) same voltage of one of the individual batteries.

34

Connecting Batteries in Series

-Two or more batteries with the positive terminal of one connected to the negative terminal of the next, with the load connected to the negative terminal of the first battery and the positive terminal of the last battery in the series.
-The voltage is equal to the sum of the voltage ratings of the individual batteries, and the current is limited to the rated current capacity of the smallest battery connected in the circuit.
-Double voltage, same capacity(amp hours)

35

Connecting Batteries in Series Parallel

-Double voltage, double capacity(amp hours)

36

Standard household volts and amps

-120/240 volts
-15 amps

37

Alternating Current

-Current which has alternately positive and negative values, occurring a specified number of times per second.
-The number is expressed in hertz(cycles per second)

38

Ammeter

-Instrument for measuring the magnitude of electric current.

39

Ammeter and Voltmeter selector switch

-A switching device that permits reading current or voltage in each of the three phases by using a single voltmeter or ammeter.

40

Ampacity

-The current-carrying capacity, expressed in amperes, of a wire, cable, or bus bar under stated thermal conditions.

41

Ampere-turn

-A unit of magnetizing force.
-The product of current flowing, measured in amperes, multiplied b the number of turns in a coil or winding.

42

Apparent Power

-A term used to describe the product of current and voltage
-Expressed in kilovolt amperes(kVA)
-The apparent power in kVA multiplied by the power factor (PF) is the real power in kilowatts(kW).

43

Battery

-A device that transforms chemical energy into electric energy in a cell with positive and negative electrodes in an electrolyte.

44

Lead Acid Battery

-A battery that uses lead as a negative electrode, lead dioxide as a positive electrode and sulfuric acid as an electrolyte.
-Nominal voltage 2 volts per cell

45

Nickel Cadmium Battery

-A battery that uses nickel oxide for a positive electrode and cadmium for a negative electrode with a n alkaline electrolyte.
-Nominal voltage 1.2 volts per cell.

46

Battery Capacity

A battery's ability to provide a specified current, for a given time period, to a specified end voltage(amp-hour rating).

47

Break-away Current

-The momentary current drawn by an electric motor to start rotation.

48

Bus

-A conductor, or group of conductors, that serves a common connection for two or more circuits.

49

Capacitance

-The property of any system of conductors and dielectrics or any device to store electrical potential energy.
-The measure of capacitance is the farad and its symbol is "C".

50

Capacitor

-A device, capable of storing electric energy, consisting of two conducting surfaces separated by dielectric material.

51

Charging Rate

-The current expressed in amperes at which a battery is charged.

52

Circuit Breaker

-A mechanical switching device capable of making, carrying, and breaking currents under normal circuit conditions.
-Automatically breaking currents under specified abnormal circuit conditions, such as those of a short circuit.

53

Circuit Breaker (Magnetic Trip)

-The portion of a circuit breaker mechanism that opens the circuit under specified abnormal current.

54

Circuit Breaker (Thermal Trip)

-The portion of a circuit breaker mechanism that opens the circuit under sustained overload but does not protect against short-circuit currents.

55

Circuit Breaker (Thermal/Magnetic Trip)

-Employ a thermal bi-metallic element having an inverse time/current characteristic for protection against sustained overloads.
-The breaker contains an instantaneous magnetic trip element for short-circuit protection.

56

Conductor

-A wire, cable or bus bar designed for the passage of electrical current.

57

Connector

-A coupling device employed to connect conductors of one circuit element with those of another circuit element.

58

Contactor

-An electro-mechanical device for repeatedly establishing and interrupting an electrical circuit.

59

Delta Connection

-A method of connecting the phases of a three phase machine in series to form a triangular configuration.

60

Dielectric

-Electrical insulator.

61

Diode

-A device that allows current to pass in one direction only.
-May be used as a rectifier

62

Eddy Current

-Circulating currents in magnetic field conductive materials caused by alternating magnetic fields.
-Represent power losses in generators and transformers.

63

Electro-Magnetic Field

-An induced magnetic field generated by the passage of an electric current through a conductor.

64

Electromotive Force (EMF)

-The force which causes current to flow in a conductor.
-The voltage or potential

65

Energy

-Capability of performing work.
-Expressed electrically in kilowatt hours(kWh).

66

Excitation

-The dc power supplied to the field coils of a synchronous generator, producing magnetic flux required for inducing voltages in the opposing member.

67

Exciter

-A device for supplying excitation to the generator field.
-May be a rotating dc, ac with rectifiers, or a static device converting ac to dc.

68

Flux

-Magnetic lines of force.

69

Frequency

-The number of complete cycles of an alternating voltage or current per unit of time.
-Expressed in hertz(Hz), cycles per second.

70

Full Load Current

-The maximum current that a circuit or device is designed to carry continuously at rated conditions.
-Also known as rated current.

71

Fuse

-An overcurrent protective device which consists of a conductor that melts and opens the circuit when current exceeds rated value for a predetermined time.

72

Ground

-A connection between an electric circuit and the earth or some conducting body serving in place of the earth.

73

Impedance

-Total opposition offered by a circuit to the flow of alternating current.
-Composed of resistance and reactance(inductive and/or capacitive)

74

Induced Voltage

-The voltage which is produced in a conductor due to change in the magnetic field surrounding it.

75

Inductance

-The property of an electric circuit that opposes any change in current flow.

76

Insulation

-Non-conductive material.

77

Kilovolt-amperes (kVA)

-1,000 volt amps (apparent power).

78

Kilovolt-amperes reactive (kvar)

-1,000 volt amps (reactive power).

79

kilowatt (kW)

-1,000 watts (real power).

80

kilowatt hour (kWh)

-Unit of electric energy.
-1 kW x 1 hr = 1 kWh.

81

Line to Line Voltage

-The voltage existing between any two phase conductors in a polyphase circuit.

82

Line to Neutral Voltage

-The voltage existing between any phase conductor and the neutral conductor.

83

Neutral

-The point in an electrical system where the voltages to all line conductors are equal.

84

Nominal Value

-Reference value selected to establish equipment ratings.

85

Ohm

-Unit of electrical resistance.

86

Ohmmeter

-Device for measuring electrical resistance.

87

Out-of-phase

-A condition in which AC voltage waves of two generating systems do not coincide.

88

Phase

-The winding of a generator that determines the number of complete voltage and/or current sine waves generated per 360 electrical degrees, as in three phase.

89

Phase Balance

-The amount of voltage difference between phase voltages under balanced load conditions.

90

Magnetic Pole

-A part of a magnetic structure called a north pole and a south pole.
-Since neither pole can exist without the opposite, they always are present in pairs.
-A generator always has an even number of poles.

91

Polyphase

-A system in which there are multiple separate complete voltage and current sine waves, each of 360 electrical degrees.
-Ex. Three phase is three complete separate sine waves spaced 120 electrical degrees apart.

92

Power Factor

-In AC circuits, the inductances and capacitances may cause the point at which the voltage wave passes through zero to differ from the point at which the current wave passes through zero.
-When the current wave precedes the voltage wave, a leading power factor results, as in the case of a capacitive load.
-When the voltage wave precedes the current wave a lagging power factor results.
-The power factor expresses the extent to which voltage zero differs from the current zero.
-PF = kW
kVA

93

Program Logic Controller (PLC)

-A solid state device capable of storing instructions to implement control functions such as sequencing, timing, counting and data manipulation to control machines and processes.

94

Protective Relay

-A device used to detect defective or dangerous conditions and initiate suitable switching or give warning.
-IEEE assigns device numbers to various types of protective relays.

95

Reactive Current

-The component of a current in quadrature with the voltage.

96

Terminal

-A device attached to a conductor to facilitate a connection.

97

Thermocouple

-A device for measuring temperatures.
-Consists of a connection between two wires of dissimilar material which generates a small voltage proportional to the temperature of the ambient.

98

Transfer Switch

-A switch designed so that it will disconnect the load from one power source and reconnect it to another source.
-Both automatic and manual transfer switches are available.

99

Transformer

-A static electric device consisting of a winding, or two or more magnetically coupled windings used to transfer power by electromagnetic induction between circuits at the same frequency, usually with changed values of voltage and current.

100

Unity Power Factor

-A power factor of 1.0.
-Characteristic of resistive load.

101

Varmeter

-A device for measuring reactive power of the circuit in which it is connected.

102

Voltmeter

-Instrument for measuring voltage.

103

Voltage Regulator

-A device which automatically controls the voltage output of a generator at its specific value.

104

Watthour

-Unit of electrical energy equal to one watt of power consumed during an hour

105

Winding

-An assembly of coils that acts to produce a magnetic flux field or to link a flux field.

106

Wye Connection

-A method of interconnecting the phases of a three phase system to form a configuration resembling the letter Y, such that one end of each of the windings is connected to a common point (the neutral point) and the other end to its appropriate line terminal.
-Same as star connection

107

Rectifier

-Permits current flow in one direction and blocks the flow of current that attempts to flow in the opposite direction.
-Like an electrical check valve.

108

Bus Bar

-A strip or bar of copper, brass or aluminium that conducts electricity within a switchboard, distribution board, substation, battery bank, or other electrical apparatus.
-Its main purpose is to conduct a substantial current of electricity, and not to function as a structural member.

109

Switchgear

-Combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment.
-Used both to de-energize equipment to allow work to be done and to clear faults downstream.
-This type of equipment is directly linked to the reliability of the electricity supply.

110

Voltage is applied to what in a relay to make it change state?

-The coil

111

Volt Ampere (VA)

-Unit used for the apparent power in an electrical circuit.
-Equal to the product of root mean square (RMS) voltage and RMS current.

112

Apparent Power

-the combination of reactive power and true power.
-the product of a circuit's voltage and current.
-Measured in the unit of Volt Amps(VA)

113

Apparent Power (S)

-the combination of reactive power and true power.
-the product of a circuit's voltage and current.
-Measured in the unit of Volt Amps(VA)

114

Apparent Power (S)

-the combination of reactive power and true power.
-the product of a circuit's voltage and current.
-Measured in the unit of Volt Amps (VA)

115

Reactive Power

-measured in volt amperes reactive (VARS).
-power stored in and discharged

116

Active (Real or True) Power

-measured in watts
-the power drawn by the electrical resistance of a system doing useful work.

117

Active (Real or True) Power

-measured in watts
-the actual power supplied to a circuit or equipment.
-includes the power supplied to do the actual work