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Electrical Studies For Trades > Exam 1: Unit 1-7 Delmar's Textbook of electricity > Flashcards

Exam 1: Unit 1-7 Delmar's Textbook of electricity Flashcards

1
Q

Direct current is described as ____

A

unidirectional

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2
Q

Current that flows in only one direction is referred to as ____ current

A

direct current

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3
Q

Current that flows in both directions is referred to as ___ current

A

alternating current

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4
Q

The Greeks were the first to discover electricity about __ years ago.

A

2500

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5
Q

Objects charged with the same type of charge will push each other away. This is referred to as ___

A

repulsion

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6
Q

Objects charged with different type of charges will draw toward each other. This is referred to as ___

A

attraction

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7
Q

An element cannot be chemically subdivided into other elements. The smallest part of an element is ___

A

an atom

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8
Q

The three principle parts of an atom are the ___

A

electron, neutron and proton

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9
Q

The part of an atom that has a positive charge is the ___

A

proton

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10
Q

The part of an atom that has a negative charge is the___

A

electron

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11
Q

The part of an atom that has no charge is the ___

A

neutron

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12
Q

The nucleus of an atom contains ___

A

neutrons and protons

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13
Q

The atomic number of an element is the number of __ in the nucleus

A

protons

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14
Q

The law of charges states that like charges ___ and opposite charges ___

A

repel, attract

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15
Q

The valence shell of an atom is the ___

A

outer

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16
Q

Valence electrons are contained in the ___ shell.

A

outer

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17
Q

A semiconductor contains ___ valence electrons.

A

four

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18
Q

What is the term for an amount of charge equal to 6.25 x 10^18 electrons?

A

coulomb

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19
Q

The force of electrostatic attraction or repulsion is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them. This is ___ law

A

Coulumbs

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20
Q

The ___ is equal to one coulomb per second

A

amprere

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21
Q

The velocity of AC through a conductor is __ the speed of light because magnetic fields travel more slowly in material dielectrics than they do through free air.

A

less than

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22
Q

A complete circuit is often referred to as a ___ circuit

A

closed

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23
Q

A ___ circuit generally occurs when the conductors leading from and back to the power source become connected.

A

short

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24
Q

___ is also referred to as electromotive force. (EMF)

A

voltage

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25
Q

The unit of electrical “pressure” that causes current to flow is called the ___

A

volt

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26
Q

Opposition to the current flow is called ___

A

resistance

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27
Q

An opposition to current flow that occurs in aleternating currents is called ___

A

impedance

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28
Q

The ___ is used to measure electrical power being used in a circuit

A

watt

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29
Q

An electrical device is listed as 3,000 watts. Approximately how many horsepower is this?

A

4- 1 horsepower= 746 watts

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30
Q

The statement, “in a DC circuit, the current is directly proportional to voltage and inversely porportional to resistance” is known as ___ law.

A

Ohm’s

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31
Q

An electrical circuit has a voltage of 50 V and a resistance of 5 ohms. What is the value of the current?

A

10A

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32
Q

An electrical circuit has a resistance of 20 ohms. The current is measured to be 6A. How many volts are applied to the circuit?

A

120

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33
Q

A static electric charge is an electric charge which __ moving

A

is not

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34
Q

Insulators are the only materials that can hold ___ stationary.

A

electrons

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35
Q

Electrostatic charges occur on ___

A

insulators

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36
Q

The current flow that occurs within a lightening bolt flows ___

A

negative to positive

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37
Q

When an object if protected by a lightening ___ is struck by a lightning bolt, it will bleed the lightning discharge to the grond before the protected object can be harmed.

A

rod

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38
Q

If a thunder cloud has a positive charge, the current in the lightning bolt will flow from the___

A

ground to the cloud

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39
Q

The lightning protection device that does not connect directly to the object to be protected is called the lightning ___

A

arrestor

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40
Q

If you walk across a carpet, touch the doorknob and get a shock, the shock was the result of a ___ static charge.

A

nuisance

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41
Q

The static charge sometimes used during spray painting is called a ___ static charge

A

useful

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42
Q

Selenium is a ___

A

semiconductor

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43
Q

The semiconductor material used as a coating on copy machine drums is ___

A

selenium

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44
Q

The static charge that accumulates on clothes in a dryer is a ___ charge

A

nuisance

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45
Q

Lodestrone is a name for a naturally occuring magnetic material that is also known as___

A

magnetite

46
Q

The angular difference between true north and magnetic north is known as the angle of ___

A

declination

47
Q

Man-made permanent magnets retain their magnetism ___ than natural magnets.

A

Longer

48
Q

Magnetism can be explained in terms of ___ spin patterns.

A

electron

49
Q

The regions formed in the molecular structure of magnetic metals is sometimes called magnetic___

A

domains

50
Q

Magnetic lines of force are called___

A

flux

51
Q

A basic law of magnetism stated that unlike poles ___ and like poles ___

A

attract, repel

52
Q

A magnet the produces a magnetic field as long as a current is flowing is called a ___ magnet.

A

electromagnet

53
Q

The strength of an electromagnet is primarily proportional to its ___

A

ampere-turns

54
Q

The measure of a material’s ability to be magnetized is called ___

A

permeability

55
Q

The measure of a material’s resistance to magnetism is __

A

reluctance

56
Q

When a magnetic materials molecules are all lined up, and increase in current flow no longer cause increases in magnetic field strength, the material has reached

A

saturation

57
Q

The amount of magnetism left in a material after the magnetizing force has stopped is called

A

residual magnetism

58
Q

In the English system of measure, magnetic strength is measured in a term called ___

A

flux density

59
Q

In the English system, the total force producing a magnetic field is the

A

magnetomotive

60
Q

In a ___ circuit, there is little resistance and a large amount of current flows

A

short circuit

61
Q

___ were used in vacuum-tube circuits many years ago and are still used today in applications involving field-effect transistors (FETs) and multirange voltmeter circuits

A

voltage dividers

62
Q

Resistors that only have one ohmic value are called ___ resistors

A

fixed resistors

63
Q

A ___ resistor is made from a compound of carbon graphite and resin bonding material

A

composition carbon

64
Q

The ___ of a resistor indicates the plus and minus limits of a resistor’s ohmic value

A

tolerance

65
Q

A ___ resistor is made by combining metal with glass and then applying it to a ceramic base as a thick film

A

metal glaze

66
Q

A ___ resistor is made by applying a film of carbon to a ceramic rod

A

carbon film

67
Q

A ___ resistor is made by winding a piece of resistive wire around a ceramic core

A

wire-wound

68
Q

What does the fourth band of color on a resistor indicate

A

tolerance

69
Q

A resistor has color bands of brown, black, red and silver. What is the resistance and tolerance of the resistor?

A

1000 ohms, 10%

70
Q

A resistor has color bands of red, violet, brown and gold. What is the resistance and tolerance of the resistor?

A

270 ohms, 5%

71
Q

True/False: All insulators perform equally well under dry, damp or wet conditions.

A

False

72
Q

True/False:The amount of voltage induced into a conductor depends on the turns of wire, the strength of the magnetic field and the speed of cutting action

A

true

73
Q

True/False: If current is flowing in a circuit containing an inductor and the power switch is opened, the magetic field surrounding the inductor collapses amd induces voltage into the inductor, resulting in a voltage spike

A

true

74
Q

True/False: When a conductor becomes heated the value of resistance decreases

A

False

75
Q

a circuit that has only one path for the current to flow is a ___ circuit

A

series

76
Q

When a circuit has only one path, the ___ is the same at any point

A

current

77
Q

A device that is designed to open and disconnect a circuit in the event of excessive current is a ___

A

fuse

78
Q

___ is the force that pushes the electrons through a resistance

A

voltage

79
Q

The amount of ___ across a resistor is proprtional to its resistance

A

voltage drop

80
Q

The total amount of resistance to current flow in a series cicuit is equal to the ___ of the resistance in that circuit

A

sum

81
Q

The current, voltage, power and resistance in a series circuit can be found by using ___ law

A

Ohm’s

82
Q

A series cicuit has a total resistance of 180 ohms and an applied voltage of 120V. What is the current flow?

A

.666A

83
Q

A series cicuit has a total resistance of 240 ohms and a current flow of 4 A. What is the applied voltage?

A

960V

84
Q

The two resistors in a series circuit have voltages of 25V and 60V. The applied voltage is___

A

85V

85
Q

A two-resistor series circuit has an applied voltage of 100V. The voltage across one of the resistors is 40V. The voltage across the other resistor is___

A

60V

86
Q

A series cicuit has two resistors. The resistors dissipate 10W and 15W. What is the total power dissipation of the circuit?

A

25W

87
Q

A three-resistor circuit has a total power of 25W. Two of the resistors dissipate 10W and 5W respectively. How much power does the third resistor dissipate?

A

10W

88
Q

A voltage __ is ised to proved different voltages between certain points in a circuit

A

divider

89
Q

A ___ must never be connected to a circuit when the circuit power is turned on

A

ohmeter

90
Q

The National Electric Code* ___ contains tables dealing with conductors for general wiring.

A

NEC 310

91
Q

The National Electrical Code* the current carrying abilities on conductors is called

A

ampacities

92
Q

The ambient air temperature considered in relation to a conductor ampacity is the temperature of the___

A

surrounding air

93
Q

The noninductive covering around a wire is the ___

A

insulation

94
Q

The insulation used on conductors cannot operate in all possible temperatures. The highest allowable temperature is called the ___ temperature

A

maximum operating temperature

95
Q

The ampacities listed in table 319.16 are based on an ambient temperature of__

A

86 degrees

96
Q

If there are more than ___ conductors in a raceway, the ampacity of the conductors must be derated.

A

three

97
Q

There are 6 current carrying conductors in a raceway that is to be installed in an area with an ambient temp of 90 degrees. It is necessar to___

A

correct for temp and derate

98
Q

the unit circular mill is equal to the __

A

diameter of the wire in mils squared

99
Q

A wire that has a diameter of 162 mils has an area of ___circular mils

A

26,244

100
Q

The longer the conductor, the more ___ it will have

A

resistance

101
Q

Materials that increase their resistance with an increase in temperature have a ___ coeficient of temp

A

positive coefficient

102
Q

In the american Engineers Handbook, the standard temperature of material resistance is ___

A

20 degrees celsius

103
Q

When a conductor is very large it may become necessary to connect them in ___

A

parallel

104
Q

When a conductor cuts magnetic lines of force, a voltage is induced into the conductor. This principle is called ___

A

electromagnetic induction

105
Q

If a voltage is being induced into a conductor by electromagnetic induction, reversing the direction of motion of the conductor will ___

A

reverse the polarity of the induced voltage

106
Q

During the period of time called the first time constant of an exponetial curve, the current will rise to about ___ % of its full value

A

63.2%

107
Q

The unit of inductance is the ___

A

henry(H)

108
Q

The time required for a current in an inductor to reach its full Ohm’s law value is called the ___ time constant

A

R-L

109
Q

A coil has an inductance of 3H and a wire resistance of 15 ohms. How long will it take for the current to reach its full value?

A

1 second. L/Rx5

110
Q

One device used for spike suppression in either direct or alternating current circuits is the ___

A

metal oxide varistor

Electrical Studies For Trades (1 decks)

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