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HVAC Excellence: Electric theory Flashcards | StudBud
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HVAC Excellence: Electric theory
HVAC Excellence: Electric theory
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A study quiz for the Electric Theory Industry Certification #HVAC
Flashcards
50 cards
F
Practice quiz
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Host live
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Questions
50
Answers
1
When the contacts become pitted what is one to do?
Sand the contacts
Replace contacts or control
Replace with a solide state relay
file the contacts
2
What determines the direction of rotation on a single phase induction motor?
The number of Stator poles
Direction of current flow through the start winding
The number of supply wires
The compass heading
3
Typical conductors are...
clay
Silicon
water
Copper, gold, silver
4
What would be the voltage on the input side of the transformer be on line #9
24v
240v
120v
60v
5
How do you rate a transformer?
VA at the secondary
Ohms at Primary and Secondary
By the car they transform into
VA at the primary
6
How do you bench check a motor for shorts or open windings?
Use an ohmmeter
Use an ammeter
Use a voltmeter
Use a wattmeter.
7
The blower motor is most likely controlled by...
The blower relay
The transformer
The supply voltage
The crankcase heater
8
An electron has a...
Neutral Charge
Harassment charge against it
Positive Charge
Negative Charge
9
one horsepower is equal to...
2100 watts
2.1 Kilowatts
240 volts
746 watts
10
What will be the total resistance of a parallel circuit?
Equal to the smallest resistance
Equal to the largest resistance
less than the smallest resistance
The sum of all resistance
11
What are the principles of a solenoed valve coil?
Pressure
Electromagnetism
time and temperature
Temperature
12
What does a step-up transformer do?
It creates more resistance
It increases the power
It increases the Voltage
It increases amperage
13
What does the electric meter on your home measure?
Wattage
Ohms
Volts
Amps
14
The minimum number of wires required between two Start/Stop push button controls are;
It depends on control design
2
1
3
15
What voltage would be found across the fuse on the tstat contacts are closed on line #10
24v
60v
120v
0v
16
what causes excessive current?
Undersized fuse
a short circuit
an open circuit
over-sized wires
17
What would voltage be across L1 and L2 in the schematic?
60v
24v
120v
240v
18
Find power when voltage is 200 and resistance is 400 ohms.
100
1000
1
10
19
Relays are generally used to control inductive loads up to
12 amps
10 amps
5 amps
25 amps
20
Find power when current is 10 amps and voltage is 120.
12
120,000,000
1.2
1200
21
How do you calculate resistance?
I divided by E
E squared by W
E divided by I
W divided by E
22
In the schematic, what would the voltage be on the energized contacts on line #8
120v
60v
0v
240v
23
2 identical 120v light bulbs wired in series with 240v will...
Burn out
Burn correctly
24
How does one reset the thermal overload contacts on a line starter?
Manual
Thermal
Automatic
Time Delay
25
Capacitors are always connected_____________to the start winding?
In series
In parallel
26
How do you determine the speed of a single phase motor?
Check the speedometer
Number of stator poles
By the supply voltage
By the Ohms
27
What is equal to 2.1 KW?
210 watts
21,000 watts
2,100 watts
21 watts
28
What is the symbol as seen in the picture?
LP switch
more crappy modern art
HP switch
T-stat in cooling mode
29
Of the following motors, which one has the most enery efficient?
SIRC
ECM
Shaded pole
PSC
30
What is the symbol as seen in the picture
T-stat in cooling mode
LP switch
Tumblr fan art
HP Switch
31
The minimum number of wires required between two Start/Stop push button controls are;
1
Depends on control design
3
2
32
What is considered a inductive load?
heat strip
start capacitor
Electric motor
current relay
33
When the contacts become pitted what is one to do?
Fill the contacts
Sand the contacts
Replace it with a solid state relay
Replace contacts or control
34
What kind of power is supplied to the residetial home?
115v single phase, three wire
240v three phase, three wire
480v three phase, three wire
240v single phase, three wire
35
Windings of a three phase motor should be checked for what?
Its cheaper to replace the motor than to test it.
All three terminals should show the same resistance.
Thepairwithhighestresistancewill indicatetheotheriscommon.
All three terminals should show different readings.
36
What statement is true about current?
Current flow is the same as voltage.
Current flow will decrease when voltage increases.
Current flow will increase when voltage increases.
Current flow will increase when resistance increases.
37
How does one reset the thermal overload contacts on a line starter?
Automatically
time and temp
Manual
thermal
38
What is the symbol as seen in the picture?
T-stat in cool mode
modern art
HP switch
T-stat in heat mode
39
A 240 volt, 3 wire circuit can be split into two 120 volt circuits.
true
false
40
Find resistance when power is 960 watts and voltage is 12.
150
15
.15
1.5
41
How do you wire in a capacitor?
In parallel
Through a Diode
In series
Through a relay
42
Which winding in a single phase motor has the most resistance?
Run
Ground
Common
Start
43
Find power when resistance is 24 and current is 10 amps.
2400
24
240
2.4
44
When using an ohmmeter, you should never connect to what?
Motor windings
A coil
A resistor
A live circuit
45
How do you change the direction of a three phase motor?
Change the position of all three wires
Replace the motor
Wire in a reversing capacitor
Change the position of any two supply lines
46
Find current when voltage is 240 and resistance is 60 ohms.
14 amps
both of these
none of these
4 amps
47
Find power when current is 5 amps and resistsnce is 5 ohms.
12.5
125
1.25
1250
48
If two light bulbs are wired in series and one bulb burns out, the other bulb will?
Stay on
Go out
49
How do you rate a transformer?
Va at the Secondary
Ohms at the primary or secondary
By the kind of Vehicle they turn into
VA at the Primary
50
Find voltage when resistance is 20 ohms and current is 6 amps.
12
1.2
1200
120
