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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
what is magnetomotive force?
cause of magnetic flux. product of number of turns in a conductor and current in the conductor. more turns more mmf
26
how does the number of turns affect the inductance of a coil
more turns more inductance
27
what are the 3 sides of a power factor triangle
hypotenuse: VA y axis: Var x axis: watts
28
describe a step up transfromer
increase voltage decrease current. more windings in the secondary
29
what are the units of measure for Xl, Xc, Z, R
ohlms
30
what is residual magnetism
Magnetism left over after a charge is gone (Short Term
31
what is the law of power with regard to the primary and secondary transformers
power in equals power out
32
how do you calculate total inductance when inductors are placed in series
sum of inductors
33
what is the difference between reactance and resistance
resistance dissipates power reactance does not
34
what type of capacitor is polarity conscious
electrolytic
35
what is impedance the equivalent to
total resistance
36
Retentivity
a materials ability to maintain magnetization after a magnetizing force is removed
37
what direction does flux flow
north to south
38
describe a step down transformer
increase current decrease voltage. more windings in the primary
39
what is the default for farads if nothing is given
P
40
in an inductive circuit what is in phase with the voltage
the resistor
41
how do you calculate the time constant for LR circuits
t = L/R
42
how may diodes in a bridge rectifier
4
43
draw a bridge rectifier
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
what is RMS
root mean squared the equivalent dc value of an ac voltage
45
when does peak voltage of a sine wave occur
90 degrees
46
what is frequency
number of complete cycles that occur in 1 second
47
why is current the same at every point in a circuit
only one path
48
how do you calculate total capacitance of capacitors in parallel
sum of the capacitors
49
how many zener diodes are needed to make a bridge rectifier
0
50
how many time constants are required to achieve maximum current flow in an inductive circuit
5
51
compare the difference between a relay and a solenoid and when are they used
a solenoid converts electrical energy to mechanical energy, and a relay is a electrical switch
52
what are the 4 types of fixed capacitors
mica ceramic plastic film electrolytic
53
what is alternation
half cycle of a sine wave. 2π
54
what is a henry
unit of measure for inductance
55
common dielectrics and their values
``` air (vacuum) 1 teflon 2 paper 2.5 oil 4 mica 5 glass 7.5 aluminum oxide 10 ceramic 1200 ```
56
define permeability
the ease at which a magnetic field can be established in a given material
57
what is the unit of measure for capacitance
farad
58
if frequency increases what happens to phase angle
increases
59
at what point does a sine wave reach half peak value
30 degrees
60
what is the left hand rule for generators
clockwise towards counter clockwise away
61
what is the equation used to find time for one cycle of a sine wave
t = 1/f
62
saturation
when a material has reached its full magnetization potential
63
how much resistance does a dielectric have
infinite
64
what are the four factors that determine the amount of voltage induced in a moving conductor
length strength speed angle
65
what is the formula used to calculate frequency
f = 1/t
66
when testing a coil with an ohmmeter what type of reading should be expected
initially a small amount of resistance that fades away
67
what is inductance
the property of a conductor to oppose a change in current
68
what is a dialectric
insulating material
69
what is the phase shift of a RC circuit
current leads voltage by 90 degrees
70
what is the value of a capacitor labeled 922
9200PF
71
how does flux density affect magnetism
the higher the flux density the stronger the magnetism
72
how do you calculate total capacitance of capacitors in series
reciprocal formula
73
inductors oppose a change in _________
current
74
handheld meters read what type of ac voltage
Vrms
75
capacitors oppose a change in
voltage

Low Voltage (9 decks)

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