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Low Voltage > AC Final > Flashcards

AC Final Flashcards

1
Q

what is the time constant formula for an rc circuit

A

t = R x C

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2
Q

how do you test a capacitor with an ohmmeter and what should you expect the results to be

A

reads as an open

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3
Q

what are the 2 measurements for farads

A

μ and P

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4
Q

what is peak to peak voltage

A

voltage from the positive to the negative peaks of a sign wave
90 degrees to 270 degrees

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5
Q

in a capacitive circuit what is in phase with the resistor

A

voltage

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6
Q

how does an inductor store energy

A

electromagnetic field

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7
Q

the arrow of a compass points?

A

to geographical north or magnetic south pole

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8
Q

how does the plate separation distance affect a capacitor

A

capacitance decreases voltage increases

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9
Q

what is the WV of a capacitor

A

the maximum sustainable voltage in dc

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10
Q

what is the period of a sine wave

A

time required for one cycle

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11
Q

what is a hertz

A

unit of measure for frequency

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12
Q

Define Reluctance

A

a materials resistance to becoming magnitized

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13
Q

what is the phase shift in an inductive circuit with regard to voltage and current

A

voltage leads current by 90 degrees

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14
Q

what is a transformer

A

two coils that use induction to reduce or increase the voltage

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15
Q

what is the percentage for the first time constant

A

63.2

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16
Q

how is an inductor constructed

A

a coil of wire around a ferrel magnetic core

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17
Q

what is the difference between the primary and the secondary of a transformer

A

ac source connects to primary winding load is connected to secondary

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18
Q

how do you calculate total inductance when inductors are placed in parallel

A

reciprocal formula

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19
Q

how is PF calculated

A

w/va x 100

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20
Q

what is the dc resistance of a normally opperating capacitor

A

capacitors block dc voltage

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21
Q

how does the size of the plates affect capacitance

A

voltage decreases capacitance increases

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22
Q

how is a capacitor constructed

A

two plates separated by a dielectric

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23
Q

how do you calculate rms

A

.707 x peak

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24
Q

how does a capacitor store energy

A

electrostatic field

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25
Q

what is magnetomotive force?

A

cause of magnetic flux. product of number of turns in a conductor and current in the conductor.
more turns more mmf

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26
Q

how does the number of turns affect the inductance of a coil

A

more turns more inductance

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27
Q

what are the 3 sides of a power factor triangle

A

hypotenuse: VA
y axis: Var
x axis: watts

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28
Q

describe a step up transfromer

A

increase voltage decrease current. more windings in the secondary

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29
Q

what are the units of measure for Xl, Xc, Z, R

A

ohlms

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30
Q

what is residual magnetism

A

Magnetism left over after a charge is gone (Short Term

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31
Q

what is the law of power with regard to the primary and secondary transformers

A

power in equals power out

32
Q

how do you calculate total inductance when inductors are placed in series

A

sum of inductors

33
Q

what is the difference between reactance and resistance

A

resistance dissipates power reactance does not

34
Q

what type of capacitor is polarity conscious

A

electrolytic

35
Q

what is impedance the equivalent to

A

total resistance

36
Q

Retentivity

A

a materials ability to maintain magnetization after a magnetizing force is removed

37
Q

what direction does flux flow

A

north to south

38
Q

describe a step down transformer

A

increase current decrease voltage. more windings in the primary

39
Q

what is the default for farads if nothing is given

A

P

40
Q

in an inductive circuit what is in phase with the voltage

A

the resistor

41
Q

how do you calculate the time constant for LR circuits

A

t = L/R

42
Q

how may diodes in a bridge rectifier

A

4

43
Q

draw a bridge rectifier

A

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiAxpLRnfHMAhVYM1IKHfIaCWgQjRwIBw&url=http%3A%2F%2Fwww.radio-electronics.com%2Finfo%2Fcircuits%2Fdiode-rectifier%2Fbridge-rectifiers-circuits.php&psig=AFQjCNFqI-ukAW7_fNXNQGwjE6cybdnbmA&ust=1464128340879855

44
Q

what is RMS

A

root mean squared the equivalent dc value of an ac voltage

45
Q

when does peak voltage of a sine wave occur

A

90 degrees

46
Q

what is frequency

A

number of complete cycles that occur in 1 second

47
Q

why is current the same at every point in a circuit

A

only one path

48
Q

how do you calculate total capacitance of capacitors in parallel

A

sum of the capacitors

49
Q

how many zener diodes are needed to make a bridge rectifier

A

0

50
Q

how many time constants are required to achieve maximum current flow in an inductive circuit

A

5

51
Q

compare the difference between a relay and a solenoid and when are they used

A

a solenoid converts electrical energy to mechanical energy, and a relay is a electrical switch

52
Q

what are the 4 types of fixed capacitors

A

mica
ceramic
plastic film
electrolytic

53
Q

what is alternation

A

half cycle of a sine wave. 2π

54
Q

what is a henry

A

unit of measure for inductance

55
Q

common dielectrics and their values

A 
air (vacuum)         1
teflon                   2
paper                   2.5
oil                         4
mica                     5
glass                    7.5
aluminum oxide  10
ceramic                1200
56
Q

define permeability

A

the ease at which a magnetic field can be established in a given material

57
Q

what is the unit of measure for capacitance

A

farad

58
Q

if frequency increases what happens to phase angle

A

increases

59
Q

at what point does a sine wave reach half peak value

A

30 degrees

60
Q

what is the left hand rule for generators

A

clockwise towards counter clockwise away

61
Q

what is the equation used to find time for one cycle of a sine wave

A

t = 1/f

62
Q

saturation

A

when a material has reached its full magnetization potential

63
Q

how much resistance does a dielectric have

A

infinite

64
Q

what are the four factors that determine the amount of voltage induced in a moving conductor

A

length
strength
speed
angle

65
Q

what is the formula used to calculate frequency

A

f = 1/t

66
Q

when testing a coil with an ohmmeter what type of reading should be expected

A

initially a small amount of resistance that fades away

67
Q

what is inductance

A

the property of a conductor to oppose a change in current

68
Q

what is a dialectric

A

insulating material

69
Q

what is the phase shift of a RC circuit

A

current leads voltage by 90 degrees

70
Q

what is the value of a capacitor labeled 922

A

9200PF

71
Q

how does flux density affect magnetism

A

the higher the flux density the stronger the magnetism

72
Q

how do you calculate total capacitance of capacitors in series

A

reciprocal formula

73
Q

inductors oppose a change in _________

A

current

74
Q

handheld meters read what type of ac voltage

A

Vrms

75
Q

capacitors oppose a change in

A

voltage

Low Voltage (9 decks)

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