Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fourth Year Electrician > Electronics Theory > Flashcards

Electronics Theory Flashcards

Electronics

1
Q

What is an example of a DC source that supplies a constant value of voltage and current for a fixed load?

A

A battery.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define “average DC” for constant output vs pulsating

A

Average value of istantaneous values recorded at even intervals over a period of time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

One cycle of an AC source is represented as _____.

A

360 Degrees.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

The frequency of a sine wave is the number of cycles that occur in one second, true or false.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do you get the rms (effective) value of voltage?

A

V(eff) = V(max) x 0.707 or V(max) / √2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How must a voltmeter be used to measure voltage?

A

In parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How must an ammeter be used to measure current?

A

In series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What could happen if the oscilloscope does not have the same reference point?

A

It may short circuit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the formula for frequency?

A

f = 1/T

T = time in seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a way to eliminate a fault current condition with the oscilloscope without isolating from ground?

A

Flip the reference lead to the other side of the impedance (load)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Semi-conductors have _____ valence electrons.

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Electronics made from semiconductor material are known as _____.

A

Solid state devices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

P-type semiconductors are considered to be _____ charged.

A

Positively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

N-type semiconductors are considered to be _____ charged.

A

Negatively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

A boran atom (trivalent atom) creates an _____ of a bond. The hole is the _____.

A

Absence.

Charge carrier.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

An antimony atom (pentavalent atom) has an _____ electron.

A

Excess

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Can you use an electronic switch as an isolating switch?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

At a PN junction, there is no _____ until there is an applied voltage.

A

Net charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Anode is the lead connected to the _____..

A

P type material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Cathode is the lead connected to the _____.

A

N type material.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

A diode allows current flow in one direction, and _____flow in the opposite.

A

Prevents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

In order to conduct, a diode requires a minimum Voltage of _____.

A

0.7 V for silicon, 0.3 for germanium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Low current diodes typically are of ____ A or less and normally mounted by _____ or _____.

A

3 A

Soldering to a circuit board

Connected to exposed terminals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Medium current diodes are usually up to _____ A and _______ mounted.

A

600 A

Stud mounted, or sometimes press fit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Press fit diodes are often used in _____ applications.

A

Rectifier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Repetitive reverse maximum voltage is the _____.

A

Instantaneous reverse bias voltage that a diode can safely withstand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

High current diodes are mounted by ______ that also function as _____.

A

Squeezing them between two conducting metal plates.

Heat sinks.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

When checking a diode with a multimeter, a typical reading would be _____.

A

0.5 mA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

To check a diode with a multimeter, where do you place the positive and negative leads?

A

Positive to anode, negative to cathode.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Arrows pointing towards a device with a light-dependant resistor, means the device is activated by _____.

A

Light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Diodes are used in the _____ of fire alarm systems.

A

Signalling devices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Current flow when no light is applied to a diode is called _____.

A

Dark current.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How do you calculate instantaneous voltage from peak/max value?

A

Multiply peak value by sine of the angle of the instantaneous voltage to be calculated.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

How do you calculate peak value from effective?

A

Divide effective by 0.707 or multiply √2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Voltage and current peak-to-peak value are symbolized how?

A

V(pp) and I(pp)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Peak to peak values in a sine wave are always _____.

A

Twice the peak value.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Can voltmeters and ammeters measure a moment in time?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

The oscilloscope is a graph of _____ over _____.

A

Voltage, time.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Oscilloscope transducers converts an input value (measured quantity) into a _____.

A

Voltage signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Heat sinks are most effective when mounted _____ to make use of the _____ effect, which means _____.

A

Vertically

Chimney

Air moves by convection over the fins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Covalent bonding means _____.

A

Each atom shares its valence electrons with adjoining atoms, making it as though each atom had 8 valence electrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

The Fluke 125B Scopemeter (is, is not) a more versatile troubleshooting and commissioning tool than a bench style oscilloscope.

A

Is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

The reference lead on a Fluke 125B Scopemeter (is, is not) grounded.

A

Is not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Using the Fluke 125B, what do you use to test ohms, continuity, diodes and capacitors?

A

Channel A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

In a series circuit, if one three resistors were removed, what would happen to the overall current?

A

Would increase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is the approximate resistance in our emmenrerds.

A

0 amps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

To verify DC Voltage value,, _____.

A

Multiply # of division x volts per division setting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

When changing the v/div setting on an oscilloscope, what is being done?

A

Only changes the scale of the measured malues.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Peak voltage = _____.

A

of divisions x volts per division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

A period is equal to _____.

A

of divisions x time per division setting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Which type of rectifier has a neutral?

A

3 phase 1/2 wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

How is current applied to the load in a half-wave rectifier?

A

Every second AC alternation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What is the simplest type of rectifier?

A

Single phase half wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

In a single phase half wave rectifier, a single diode is connected in (series, parallel) with the load

A

Series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

The DC output of a single phase half wave rectifier is _____ the peak voltage.

A

31.8%

56
Q

Forrmulas for DC voltage in a single phase half wave rectifier.

A

V (dc) = V peak x 0.318

Or

V (dc) = 1/π

57
Q

In a single phase half wave rectifier, the peak load voltage is _____ the peak supply voltage.

A

The same as

58
Q

The ripple frequency of a single phase half wave rectifier is _____.

A

The same as the supply

59
Q

The diode current in a single phase half wave rectifier is _____.

A

Same as the load current

60
Q

Full wave rectification is when _____.

A

The load sees a voltage during both alternations

61
Q

What is the conversion factor for a single phase full wave rectifier?

A

0.637 of the peak value voltage

62
Q

What is the average DC voltage output of a single phase full wave rectifier?

A

63.7% of peak instantaneous voltage

63
Q

What are the formulas for the value of voltage output for a single phase full wave rectifier?

A

V(DC) = V(peak) x 0.637

V(DC) = V(peak) x 2/π

64
Q

The half-wave rectifier splits an AC waveform into _____ that add together to equal the input voltage.

A

Postive and negative half cycles

65
Q

The average value of a 120 V(ac) sine wave is _____.

A

0 V

66
Q

What is the rating of a diode represents reverse bias limit?

A

V(rrm)

67
Q

What does a suppression diode do?

A

Control the cemf spike when an inductive DC circuit is opened.

68
Q

If a silicon diode is connected in series to a load, and a voltage is applied to the circuit, what would the voltage reading at the diode be if the diode is forward bias?

A

0.7 V

69
Q

Conductors have how many valence electrons?

A

1-3

70
Q

Insulators have how many valence electrons?

A

5-8

71
Q

What percentage of the peak voltage in a three-phase half wave rectifier is the output voltage?

A

82.7%

72
Q

What percentage of the peak voltage in a three-phase full wave rectifier is the output voltage?

A

95.5%

73
Q

In which rectifier must a 4-wire wye connection be used?

A

Three phase half wave

74
Q

Is a neutral required in a three phase half wave rectifier?

A

Yes

75
Q

What is the ripple frequency in a three-phase half wave rectifier?

A

3x the supply

76
Q

What is the ripple frequency in a three-phase full wave rectifier?

A

6x the supply

77
Q

In a three-phase half wave rectifier, the peak load voltage is equal to the ______ voltage.

A

Peak phase (line to neutral)

78
Q

In a three-phase half wave rectifier, when one diode is conducting the other two must ______.

A

Block the line to line voltage

79
Q

What is the load current of each diode in a three phase half wave rectifier?

A

1/3 of the load current

80
Q

The assembly of a three phase full wave rectifier has how many leads? What are they?

A

Five.

3 AC input leads

2 DC output leads

81
Q

Three sets of modular assemblies containing two diodes each could be used as a ________ rectifier, and would be mounted to a _____ for heat dissipation.

A

Three phase full wave.

Heat sink

82
Q

In a three phase full wave rectifier, the peak load voltage is equal to ______.

A

Peak line voltage

83
Q

How do battery chargers restore the electrical charge to storage batteries?

A

Rectifying AC voltage to provide DC voltage

84
Q

Battery chargers are rated in what capacity?

A

Current

85
Q

What is “trickle charge”?

A

Charging at a slow rate, ie a 6 or 12 V battery @ 2 A

86
Q

A fast charge would be __ V at __ A

A

12 V at 10 A

87
Q

What are the two main components of a battery charger?

A

A transformer with adjustable tap settings

A rectifier

88
Q

The secondary of a transformer in a battery charger is connected in _____ with ______ windings.

A

Parallel

Two center-tapped

89
Q

Connecting the transformer secondary of a battery charger in parallel achieves what?

A

Increased current capacity with lower cost (smaller conductors)

90
Q

Four of the eight ends of the transformer secondary windings are connected solidly to the ______ rail of the rectifier.

A

Negative rail

91
Q

Four ends of the transformer secondary windings are connected to the _____ of four _____.

A

Anodes

Press-fit diodes

92
Q

What might happen if two diodes in parallel aren’t closely matched?

A

One diode might carry more of the load and cause it to overheat

93
Q

The diodes in the rectifier of a battery charger are press-fit into a _____ that forms part of the ______ rail.

A

Heat sink

Positive

94
Q

In a center-tapped rectifier of a battery charger, each leg carries ____ of the load current, _____ of the time.

A

1/2

1/2

95
Q

If two sets of two 25 A parallel-connected diodes are used in the rectifier of a charger, what is the load current capacity?

A

100A

96
Q

Overcurrent circuit breakers on a battery charger are connected in _____.

A

Parallel

97
Q

When does the current transfer in a battery charger take place?

A

When the charger voltage is higher than the battery voltage.

98
Q

Why is the current greater when a battery has a lower voltage? When it is nearing full charge the current is less… what is this process called?

A

The difference between peak charger voltage and battery voltage is higher.

Tapered charging

99
Q

If the peak output voltage of a battery charger is normal but the DC avg is half the expected value, what is most likely the issue? What does this do to the waveform

A

One pair of diodes has failed.

It appears like that of a half wave rectifier

100
Q

Corrosion is an ______-______ process.

A

Electro-chemical

101
Q

What occurs by an ‘anodic’ reaction?

A

Change from a metallic form to combined form (ie iron oxide

102
Q

What does an anodic reaction produce?

A

Free electrons

103
Q

Does corrosion occur at the cathode?

A

No

104
Q

Where does corrosion occur?

A

At the anode

105
Q

What is cathodic protection?

A

Connection of an external anode to the metal being protected - passes a DC current to make all protected metals cathodic, so they do not corrode.

106
Q

What are the four parts of the corrosion process?

A

Anode, cathode, electrolyte, metallic path.

107
Q

When does corrosion occur?

A

When all four parts are present.

108
Q

Where does current flow by chemical means in relation to the anode in a corrosion cell?

A

From the surface of the Anode metal to the electrolyte

109
Q

An oxidation reaction occurs when _____.

A

Current is carried by the metal moving into solution as positively charged ions

110
Q

Where does current flow by chemical means in relation to the cathode in a corrosion cell?

A

From the electrolyte to the metal

111
Q

What is a reduction reaction?

A

The cathode gaining electrons from the electrolyte

112
Q

Where do ions flow?

A

In the electrolyte

113
Q

What is the electrolyte?

A

Any material in contact with both the anode and cathode that allows oxidation and reduction reactions.

114
Q

What is the metallic path?

A

Any metal that completes a path between the anode and cathode, allowing electrons to flow

115
Q

Electron flow must be present for _____-_____ corrosion to occur

A

Electro-chemical

116
Q

Can a pipeline be used as the metallic path in a cathodic protection system for the pipeline itself?

A

Yes

117
Q

What are the two most common types of cathodic protection systems?

A

Sacrificial (galvanic) anode

Impressed current system

118
Q

What are three common materials used for the sacrificial anode type of system?

A

Aluminum

Zinc

Magnesium

119
Q

What are some applications of a cathodic protection system?

A

Storage tank

Potable water distribution

Sewage lifts

Steel pipe

Pier support

Concrete reinforcing steel

120
Q

Cathodic protection rectifiers are powered by __ equipment that provide __ for what type of protection systems?

A

AC current

DC current

Impressed current systems

121
Q

The seven parts of a rectifier used for cathodic protection system are:

A

1: Adjustable step down transformer
2: Rectifier stacks
3: Shunt to measure output current
4: Meters to indicate output current and voltage
5: Circuit breakers
6. Lightning arresters
7: Transformer tap connections

122
Q

What are the two general types of rectifier stacks?

A

Selenium plates

Silicon diodes

123
Q

Which type of rectifier stack should be used for high current & high voltage?

A

Silicon diode

124
Q

A selenium plate unit is more efficient than a silicon diode unit. T or F

A

False

125
Q

Surge protection is provided to silicon diode units via _____ _____ _____.

A

Metal Oxide Varistors

126
Q

On manually controlled rectifier units, the center tap is the _____ connection and the negative/positive lugs are the _____ from the stacks.

A

Input

Output

127
Q

Automatic rectifiers are sometimes used when _____ and _____ is changing.

A

Structure size

Cathodic protection circuit resistance

128
Q

How can an automatic rectifier be controlled?

A

Potential control, current control, voltage control

129
Q

Can a current or voltage controlled rectifier be used in an elevated water tank?

A

No

130
Q

Current controlled rectifiers would be used in what type of situation?

A

Changing cathodic protection circuit resistance

131
Q

Meters and/or a shunt would be located between the _____ and the ______.

A

Stacks

Output lug

132
Q

What part(s) of a cathodic protection system are considered the ‘input’ section?

A

Supply circuit, incoming circuit breaker

133
Q

What part(s) of a cathodic protection system are considered the ‘output’ section?

A

Rectifier circuit, anodes, instrumentation and reference leads

134
Q

What section of the CEC covers cathodic protection systems?

A

Section 80

135
Q

What materials are normally used as an anode in an impressed current system?

A

Graphite, high silicon cast iron, platinum or mixed metal oxide

136
Q

What is usually used as the earth contact backfill to provide a uniform electrolyte?

A

Coke breeze or calcined fluid petroleum coke

137
Q

What must be done to prevent the copper lead wire from becoming part of the anode system?

A

Special insulation

Fourth Year Electrician (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions