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A Test Review > Rules, Definitions, Acronyms, & Formulas > Flashcards

Rules, Definitions, Acronyms, & Formulas Flashcards

1
Q

Voltage remains the same in a _____.

A

Parallel circuits ____ remains the same.

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2
Q

Current remains the same in _____ ckt.

A

Series ckt ____ remains the same.

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3
Q

Formula to find resistance in a series ckt :

A

Rt = R1 + R2 + R3 + R4…

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4
Q

To find resistance in a parallel ckt

A

Reciprocal

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5
Q

Product over sun

A

A method used to find resistance when you have two values in a parallel ckt

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6
Q

How do you find inductance in a parallel ckt?

A

Use the same as reciprocal

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7
Q

Formula for capacitive reactance

A

XC = 1/2(3.14)(f)(c)

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8
Q

Formula for inductive reactance

A

XL = 2(3.14)(f)(l)

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9
Q

Stationary part of a motor is called a ___.

A

Stator is the _____ part of an AC motor.

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10
Q

Rotating member of an AC motor is called ___.

A

Rotor is the ____ part of an AC motor.

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11
Q

The stationary part of an D.C. motor is a ____.

A

Field frame is the ___ of D.C. Motor.

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12
Q

Three types of DC motors:

A

Shunt

Series

Compound

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13
Q

Formula for synchronous speed

A

RPM = 120 x F

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14
Q

Formula for the actual speed of a motor:

A

Synchronous speed - slip

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15
Q

The average of all the instantaneous AC values during 1/2 cycle. The average value of a complete cycle is 0

A

AC Average

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16
Q

The AC level of power that will produce the same amount of heat produced by an equivalent DC power. Also referred to as the RMS (root means square) value

A

AC effective

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17
Q

The speed of the rotating field (sychronous) determined by the frequency and the number of poles

A

AC RPM

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18
Q

speed of the rotor in an AC motor determined by the load. Close to synchronous speed at no load and matches the nameplate at full load

A

Actual Speed

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19
Q

ease at which AC current flows in a circuit

A

Admittance

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20
Q

Maximum value that the current at full field and full armature voltage for a particular design

A

Amplitude

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21
Q

The speed of the armature at full at full speed and full armature voltage for a particular design.

A

base speed

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22
Q

the movement of electrons in a circuit as they are influenced by a magnetic field.

A

basic induction

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23
Q

max torque an AC motor developed under load without an abrupt drop in speed. the rotor will have a 45 degree phase angle

A

breakdown torque

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24
Q

the ability to store energy in an electrostatic field

A

capacitance

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25
Q

ability of a component to conduct

A

conductance

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26
Q

the speed of an armature determined by the design of the motor itself. Max is at full armature and full field

A

DC RPM

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27
Q

A potential or energy per unit of charge measured in volts

A

electromotive force

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28
Q

the direction of electrons as they flow from valence ring to valence ring, from negative to positive

A

electron flow

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29
Q

the weakening of the stationary field in a DC motor which will allow an increase in armature speed with loss of torque

A

field weakening

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30
Q

The force field of a magnet with the strongest point at the poles. the field surrounding a conductor with current flowing on it.

A

Flux

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31
Q

Number of magnetic flux lines per cross sectional area.

A

flux density

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32
Q

total opposition to current flow in an AC circuit, combining the counter voltage (XL) and the resistance (R)

A

impedance

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33
Q

The ability to store energy in an electromagnetic field.

A

inductance

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34
Q

the force that is produced by the by the magnetic lines in a circuit

A

magnamotive force

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35
Q

the ability of a material to keep the magnetic domains aligned and maintain the residual magnetic force.

A

permeance

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36
Q

the process of inducing current and voltage in a conductor as a direct result of current flow in another

A

mutual induction

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37
Q

the ability of a material to allow the passage of magnetic lines of flux as compaired to air.

A

permeability

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38
Q

a difference in charges between two points. A negative potential has an excess of electrons and a positive potential has an absence of electrons

A

potential

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39
Q

the amount of work that can by a load in a standard amount of time, usually one second. Can be useful (wall heater) or wasted (bad connection)

A

power

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40
Q

the ratio of true power (KW) to apparent power (KVA). AC motors with an uncorrected ___ run at 80%

A

power factor

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41
Q

the opposition to current flow in a DC ckt

A

resistance

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42
Q

opposition to current low in an AC ckt & the opposition to change. it is counter voltage that is induced in the ckt and can be inductive or capacitive

A

reactance

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43
Q

the opposition to magnetic lines of flux or a magnetic field

A

reluctance

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44
Q

an AC ckt where the XL and the XC have cancelled each other by being equal and the reactance is zero

A

resonance

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45
Q

AC: the interaction between the rotating field in the stator and the induced field in the rotor.
DC: the interaction between the stationary field (shunt, series, both) and the field in the armature.

A

rotation

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46
Q

the frequency induced in the rotor determined by the rotating field in the stator.

A

rotor frequency

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47
Q

inducing a counter voltage to the source determined by the direction of the flux as the source current flows in a ckt

A

self induction

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48
Q

a multiplier used on a nameplate that allows a motor to run over the rated current and horsepower for short periods

A

service factor

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49
Q

the difference in the speed of the rotor and rotating field in the stator

A

slip

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50
Q

the speed of the rotating field in a polyphase stator determined by the source frequency and the number of poles

A

synchronous speed

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51
Q

a turning or twisting force measured in foot pounds

A

torque

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52
Q

ELI the ICE man (inductive circuits - L)

A

voltage (E) leads the current (I)

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53
Q

ELI the ICE man * capacitive ckt’s - C)

A

current (I) leads the voltage (E)

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54
Q

the relationship and the effect of current, voltage, and resistance in a ckt. 1 volt applied to 1 ohm allows 1 amp of current flow

A

ohms law

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55
Q

induced current in any ckt creates a field that is always in such a direction as to oppose the field that caused it (CEMF)

A

Lenz’s Law

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56
Q

the sum of the voltage drops around any closed loop in a ckt is equal to the sum of EMF’s in that loop

A

Kirchhoff’s law = voltage

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57
Q

the sum of the current arriving at any junction point in a ckt is equal to the sum of the current leaving that point

A

Kirchhoff’s law = current

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58
Q

I (squared) R losses due to the resistnace of the winding dissipated in heat and temperature coefficient.

A

Copper loss (heat loss)

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59
Q

power consumed in an AC ckt to align molecules (magnetic domains) in a magnetic material each time the polarity changes.

A

hysteresis

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60
Q

lines of flux that miss the core and leak into space

A

flux leakage

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61
Q

circulating currents in the core that consume power. laminating the core will reduce the cross sectional area and reduce the current in the material

A

eddy currents

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62
Q

the point at which the core cannot hold any more magnetic lines of flux due to any increase in current

A

saturation

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63
Q

A rotor has ___, while an armature has a ____

A

(Slip rings) are found in a ___, while a (commutator) is part of a ___.

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64
Q

A rotor produces its poles through ___, while an armature produces its poles through a connected ____.

A

(Induction) creates poles in a ____ of a motor, while a (connected power supply) produces the poles in a an _____.

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65
Q

A ckt that is 10 times more resistive than it is inductive is considered ____, whereas a ckt that is 10 times more inductive than it is resistive is considered ____.

A

purely resistive

purely inductive

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66
Q

A magnetic field will surround a conductor as a direct result of ___ in that conductor & is proportional to the amount of ___.

A

current

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67
Q

the four factors that determine capacitance can be found by using the acronym D.A.N.S.

A 
D = dielectric matter
A= area of the plates
N= number of the plates
S= spacing of the plates

these four factors determine ____.

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68
Q

The four factors that determine inductance of an inductor by using the word CoNTroL

A

C = cross section of core
N= number of turns
T= type of core
L=length of the coil

these four factors determine ____.

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69
Q

measurement of current

A

amp

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70
Q

measurement of capacitance

A

Farad

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71
Q

measurement of inductance

A

Henry

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72
Q

measurement of conductance

A

MHO

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73
Q

measurement of resistance

A

ohm

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74
Q

measurement of potential

A

volt

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75
Q

measurement of power

A

watt

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76
Q

“C” = ___

A

symbol for capacitance

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77
Q

“E” = ____

A

symbol for voltage

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78
Q

“G” =

A

symbol for conductance

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79
Q

“FLA” =

A

symbol for full load amps

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80
Q

“H”

A

symbol for Henry

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81
Q

“I” =

A

symbol for current

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82
Q

“LRA” =

A

symbol for locked rotor amps

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83
Q

“P” =

A

symbol for power

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84
Q

“R” =

A

symbol for resistance

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85
Q

“SF” =

A

symbol for service factor

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86
Q

“X” =

A

symbol for reactance

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87
Q

“Z” =

A

symbol for impedance

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88
Q

“CEMF” =

A

symbol for counter electro motive force

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89
Q

“EMF” =

A

symbol for electro motive force

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90
Q

“MMF” =

A

symbol for magna motive force

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91
Q

I x E , I(sq) x R , E(sq) / R

A

formulas for power (P)

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92
Q

I x R , P/I , sq root of (P x R)

A

formulas for volts (E)

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93
Q

P/E , E/R , sq root of (P/R)

A

formulas for amps (I)

94
Q

E/I , E(sq)/P , P/I(sq)

A

formuals for ohms (R)

95
Q

Current in amperes is ____ to the voltage in volts and ____ to resistance in ohms

A

directly proportional

inversely proportional

96
Q

when current finds an alternate path back to the source, rather than taking the path through the load, it is called a ____.

A

short circuit

97
Q

current is _____ proportional to resistance in a ckt.

A

(“inversely” proportional:) the relationship btwn ____ and ____ in a ckt.

98
Q

When the negative terminal of one battery is connected to the positive terminal of the next battery in a series ckt, it causes the ____ to be added to the next.

A

(voltage) is added when the negative terminal of one battery is added to the positive terminal of the next in a ____ type of ckt.

99
Q

If power sources are connected so that their polarities are not in the same directions, they will oppose each other

A

E(total) = E(larger) - E(smaller)

100
Q

the total ___ in a ckt always equals the source voltage.

A

total (voltage drop) in a is always equal to the ____.

101
Q

If a ckt is ___, no current will flow.

A

if a ckt is (open) no _____ will flow.

102
Q

___ is constant in a series DC ckt.

A

current is constant in ____ DC ckt

103
Q

the current through any resistor is series with source voltage is equal to the total ____.

A

Total (current) is equal to source voltage when current flows through any resistor in ____ type of ckt.

104
Q

The ___ across a resistor is equal to I x R regardless of the type of circuit.

A

“voltage drop” is equal to ____ (formula) regardless of the type of ckt

105
Q

____ delivered to circuit is the measure of the amount of work done by a circuit per unit of time

A

power

106
Q

as the current through a series circuit decreases, the total power dissipated in each component decreases.

A

relationship between current and power in a series ckt

107
Q

The purpose of ____ in an electrical ckt is to cause electrons to flow.

A

voltage

108
Q

An open in any branch of a parallel ckt will cause a decrease in total ____.

A

current

109
Q

for a ckt to be considered a parallel ckt, there must be at least ____ of current flow

A

two paths

110
Q

the unit of measurement of electrical power is the ____

A

watt

111
Q

___ is a special type of adjustable resistor that is used to adjust the current in a branch of a ckt

A

rheostat

112
Q

Three way switches are also known as ____

A

single pole, double throw switches SPDT

113
Q

three way and four way switches shall be so installed that all switching is done in the ______

A

ungrounded ckt conductors

114
Q

Fuses and ckt breakers are primarily designed to protect ____, ____, ____.

A

conductors, components, and equipment are protected by fuses and ckt breakers.

115
Q

overcurrent devices such as ckt breakers and fuses are connected in ____ with the load.

A

series

116
Q

Find the circular mils of a wire

A

diameter squared

117
Q

____ is generated anytime current flows through a wire.

A

heat

118
Q

a condition of no resistance and very high current is called a _____

A

short ckt

119
Q

A ___ is an unintentional connection between an ungrounded conductor and any grounded raceway, box, enclosure, or fitting

A

ground fault

120
Q

A GFCI will not protect a person from ____ contact hazards.

A

line to line

121
Q

A GFCI will protect a person from _____ and ___ contact hazards.

A

line to neutral

line to ground

122
Q

A GFCI (ground fault circuit interrupter is a device intended for the protection of personnel that functions to de-energize a ckt or portion thereof within an established period of time when a current to ___ exceeds ___ ma.

A

ground / ma

123
Q

A(n) ____ is the operation of equipment in excess of normal, full-load rating or of a conductor in excess of rated ampacity, that when it persists for a sufficient length of time, would cause damage or dangerous overheating.

A

overload

124
Q

____ is the maximum current, in amperes, that a conductor can carry continuously under the conditions of use w/o exceeding its ____ rating.

A

Ampacity

temperature rating

125
Q

Conductors of branch ckt’s shall be sized to allow for maximum voltage drop of ___ supplying light, heat, or power & the maximum voltage drop allowable for feeders & branch ckt’s combined shall not exceed ___.

A

3%

5%

126
Q

In a three wire, single phase system, the line to line voltage is ____ volts.

A

240 volts

127
Q

In a three wire single phase system, the size of the neutral conductor is ____ % of the line conductors.

A

100%

128
Q

The single greatest advantage of alternating current is the fact that AC current can be ____ & DC current cannot.

A

transformed

129
Q

Copper losses are the I^2 x R in the windings of the _____ and ____.

A

field and armature

130
Q

____ are currents induced in metals by changing magnetic fields and can produce enough heat in high current ckts to melt the insulation surrounding the conductors.

A

eddy currents

131
Q

____ affects metals made of magnetic materials such as iron and steel caused by molecular friction from rapid magnetization and demagnetization, also producing heat.

A

Hysteresis.

132
Q

The voltages of a three phase system are spaced ____ apart.

A

120 degrees

133
Q

The maximum amount of voltage attained by the wave form.

A

peak value

134
Q

The RMS value of voltage will produce as much power as a like amount of ____.

A

DC voltage

135
Q

The total opposition to current flow in an AC circuit is most accurately referred to as the circuit’s ____.

A

impedance.

136
Q

Two metal plates separated by a dielectric best describes a ____.

A

capacitor

137
Q

A magnetic field is created around a conductor whenever ____.

A

current flows through a conductor.

138
Q

The maximum points of the sine wave are at ___ and ___.

A

90 and 270 degrees

139
Q

The minimum points of a sine wave are at ___ and ___.

A

0, 180, and 360 degrees

140
Q

Skin effect is proportional to ____.

A

frequency

141
Q

Skin effect can be reduced by using conductors with ____.

A

large surface area

142
Q

In a wye connected system: E-line = ____

A

E-phase x 1.73

120v x 1.732 = 208v

143
Q

In a delta connection E-line = ____

A

E-phase

480v = 480v

144
Q

The ration of true power to apparent power

A

power factor

145
Q

Single phase alternating voltage can be produced by rotating a magnetic field through the conductors of a ____.

A

stationary coil

146
Q

Neutral current in a three-wire, single phase system will flow only when there is a(n) ____.

A

unbalance

147
Q

An inductor stores energy in the form of a ____.

A

magnetic field

148
Q

A three phase power source can be produced by rotating a magnetic field through _____.

A

3 sets of coils arranged 120 degrees apart.

149
Q

In an AC ckt, current and voltage are in phase at the ____.

A

resistors

150
Q

As an AC ckt adds parallel branches for current to flow, the ckt’s impedance will ____.

A

decrease

151
Q

Poor power factor in a plant is normally caused by ____.

A

inductive loads

152
Q

An electric device that uses electromagnetism to change voltage from one level to another level or to isolate one voltage from another.

A

transformer

153
Q

The power in a single phase ckt drops to zero ___ times in a cycle.

A

two

154
Q

Receptacles in dwelling units shall be installed such that no point measured horizontally along a floor line of any wall space is more than ____ from a receptacle outlet.

A

6 feet

155
Q

A list of detailed job requirements under which all work must be performed is known as ____.

A

specifications

156
Q

Bridge type ____ produce full-wave ____. both the positive and negative half of the AC wave form are changed to DC.

A

rectifier / rectification

157
Q

____ ckt breakers are the most common type found in the electrical business.

A

molded case

158
Q

In a wye-connected system, the only current that flows in the neutral wire is the ____.

A

unbalanced current

159
Q

In a 3-phase ckt, power varies during a cycle, but never ___.

A

falls to zero

160
Q

Before the aught sizes start, the largest size building wire listed in wire gauge number is ___.

A

1 AWG

161
Q

The primary winding of a transformer is connected to the ____.

A

power line

162
Q

The secondary winding is connected to the ____.

A

load

163
Q

Dry-type transformers installed indoors and rated 112.5kVA or less shall have a separation of at least ___ from combustible material unless separated from the combustible material by a fire resistive, heat-insulated barrier.

A

12”

164
Q

____ have only one winding which is used as both the primary and the secondary.

A

autotransformers

165
Q

The NEC requires that a high leg be identified by an ____ or by tagging.

A

orange wire

166
Q

Transformers are rated in ____ because the true power is determined by the ___ of the load.

A

kilo-volt-amps / power factor

167
Q

Three phase transformer systems require about ____ than single phase systems to deliver the same amount of power to all loads.

A

25% less copper.

168
Q

The current carrying capacities for most solid-state relays is less than ____ amperes.

A

ten

169
Q

Section ___ of the NEC requires bonding all non current-carrying metal parts of the electrical distribution system together with inter-connenction to the grounded service neutral conductor or other grounded service conductor to from the ground fault path return.

A

250

170
Q

Approved grounding electrodes are:

A

metal underground water pipe, metal frame of the building or structure, concrete encased electrodes, ground ring, and supplemental electrodes.

171
Q

This must be run to each service disconnecting means, bonded to service disconnecting means enclosure, routed with phase conductors, & must be sized no smaller than the grounding electrode conductor (GEC).

A

grounded service conductor

172
Q

In the service equipment panel, this should be used as the common tie point for all other grounding and bonding of the equipment.

A

grounded neutral busbar

173
Q

From the point of entry or attachment to the building, to a bus in the service equipment enclosure, this is the common tie point for all ground fault return on both the supply and load sides of the service equipment

A

grounded service entrance neutral conductor

174
Q

the grounding electrode establishes an electrical connection to ____.

A

earth

175
Q

the maximum number of auxiliary contacts which can normally be installed on a magnetic contactor is ___.

A

eight

176
Q

AC ckts of ____ volts or more must be grounded in accordance with NEC section ____.

A

50 / 250

177
Q

devices which are activated by a magnetic field produced by an electrical current in a conductor.

A

electromechanical devices

178
Q

a discrete switch (on/off) used to control the level in a tank is called a ____.

A

float switch

179
Q

NEMA AC motors are designed ___ hertz power.

A

60

180
Q

Motor power is rated in ___ or ____.

A

horsepower / watts

181
Q

A relay that uses a resistive heating element to open a set of contacts.

A

thermal overload

182
Q

a condition that causes the current to rise hundreds of times higher than normal at a very fast rate.

A

short ckt

183
Q

an unintentional connection between an ungrounded conductor and any grounded raceway, box, enclosure, or fitting.

A

ground fault

184
Q

a three position switch that can be used to manually change the direction of a three phase motor

A

drum switch

185
Q

These generally step down the main line voltage to a control voltage of 120 or 24 volts AC.

A

control transformers

186
Q

the most common system for industrial control applications

A

grounded system

187
Q

a term used to describe a relay which enables the energy in a high powered ckt to be switched by the low powe ckt in a control system

A

interposing relay

188
Q

relays that protect the motor of a motor ckt

A

overload relays

189
Q

damage may occur to an AC motor if the supply voltage is varied more than ___ above or below the rated nameplate voltage

A

10%

190
Q

electrical ratings including voltage rating, current rating, frequency rating, and phase are listed on the ___

A

motor nameplate

191
Q

a single phase AC motor that includes a run winding and a resistive start winding used in applications such as fans, business machines, machine tools, and centrifugal pumps where starting is easy.

A

split-phase motor

192
Q

the direction of rotation of a 3 phase motor can be reversed by interchanging ___

A

any two of the 3 phase power lines to the motor

193
Q

the direction of rotation of a single phase motor can be reversed by switching the ___

A

two start leads, reversing the current and the poles in the rotor

194
Q

a motor that can be operated on either single phase AC or DC power

A

universal motor

195
Q

the amount of current drawn when the motor is connected to the maximum load the current is designed to drive

A

full-load current

196
Q

the rotating member of a DC generator is called the ___.

A

armature

197
Q

the stationary part of an alternator

A

stator

198
Q

the horsepower rating for a 3 phase motor is about ____ than a single phase motor of about the same physical size.

A

150% greater

199
Q

In split phase motors, when power is first applied, both the run winding and the start winding are energized. When the motor reaches approx ___ of the full speed, the ___ opens, disconnecting the start winding from the ckt.

A

75% / centrifugal switch

200
Q

____ motors have the start winding and run winding connected at all times. they do not need a ____ to remove the start winding, thus increasing the running torque.

A

capacitor- run / centrifugal switch

201
Q

a switch that opens to disconnect the start winding when the motor reaches a certain preset speed and reconnects the start winding when the speed falls below a preset value

A

centrifugal switch

202
Q

the voltage rating that is the optimal voltage that should be connected to a motor for best operating performance

A

motor nameplate rating

203
Q

a motor breaking technique when the motor is reconnected as a DC generator after it is disconnected from the main power

A

dynamic breaking

204
Q

All AC motors have high initial ___ that can cause breakdown on the power distribution system.

A

inrush currents

205
Q

The most common motor used in commercial and industrial applications.

A

3 phase motor, squirrel cage induction motor

206
Q

ladder diagrams are read like a book from left to right with ___ on the left and ___ on the right.

A

input / output

207
Q

devices that start a load are usually connected in ___ while devices that stop a load are connected in ____.

A

parallel / series

208
Q

The part of the ladder diagram that contain control devices such as contact, coils, switches.

A

rungs

209
Q

A ___ must be contained in every rung of a ladder diagram.

A

coil

210
Q

a device that can sense the force exerted by pressure.

A

pressure switch

211
Q

the most common manual operator interface device used in motor control applications is the ___.

A

push button

212
Q

often referred to as low voltage release because the lower voltage in the control ckt is switch by the input pilot device. Also called automatic control because no operator action is required for an input signal and activation of the load.

A

two wire control

213
Q

the most commonly used motor starter control, requires three wires between the input and the output. sometimes called semi-automatic control because operator action is required to initiate an input signal.

A

three wire control

214
Q

a relay which maintains its contacts in the activated state without being continuously energized by means of a mechanical latch or residual magnetism in the coil’s core.

A

latching relay.

215
Q

the dc motor is manually started with a ___.

A

rheostat

216
Q

____ convert mechanical energy in electrical energy

A

generators

217
Q

The most common indicating devices used in a motor control system is the ____.

A

pilot light

218
Q

an electronic device for controlling the rotational speed of an AC motor by changing the frequency of the electrical power supplied to the motor.

A

VFD

219
Q

Fire alarm initiating devices include:

A

thermal detectors, duct detectors, smoke detectors, manual switches, and flow switches

220
Q

Fire alarm notification devices include:

A

horns, strobes, speakers, and annuciators

221
Q

Auxiliary control functions include :

A

fans, door holders, and elevators

222
Q

Two basic types of of smoke detectors:

A

ionization and photo electric

223
Q

Two basic types of thermal detectors:

A

fixed temperature / rate-of-rise

224
Q

All initiating and notification devices must be supervised by the ___.

A

Fire Alarm Control Panel (FACP)

225
Q

Whether they are manual or automatic, smoke or thermal, flow or tamper, all initiating devices are also considered ___ devices.

A

monitoring type

226
Q

For a STRAIGHT PULL, the critical measure of the pull box is its overall length from the raceway entry wall to the raceway exit wall opposite, shall be greater than or equal to __ the trade diameter of the largest raceway being used.

A

8 times

227
Q

For an ANGLE PULL, the length and height of the box from the raceway-entry wall to the sidewall opposite must be a minimum of ____ the trade diameter of the raceway.

A

6 times

228
Q

the corruption of the fundamental sine wave at frequencies that are multiples of the fundamental.

A

harmonic distortion

229
Q

Overheated transformers, neutral conductors, & other electrical distribution equipment, nuisance tripping of ckt breakers, loss of synch on timing ckts that operate on a clean zero crossover sine wave trigger are all symptoms of ____.

A

harmonic distortion

230
Q

a high voltage, short duration spike on any of the utility phase conductors.

A

transient impulse

231
Q

___ can be as high as several thousand volts and can do tremendous damage to digital equipment. They can be caused by switching operations or weather.

A

transients

232
Q

Sophisticated electrical devices that use utility power to synthesize a power source isolated and dedicated to the critical load equipment.

A

Uninterruptible power supplies

A Test Review (1 decks)

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