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Single-Phase, Three-phase, Circuit Protection > Practice Exam > Flashcards

Practice Exam Flashcards

1
Q

What is the unit of measurement for electrical power and what is the formula for finding it, in a resistive type circuit?

A

P = E x I

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2
Q

What is the formula for finding the total resistance of three loads connected in parallel?

A

1/R1 + 1/R2 + 1/R3 = 1/Rt

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3
Q

The ____________ enforces the Canadian electrical code?

A

CSA

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4
Q

Before an electrical contractor can install any electrical service to any type of HVAC & R equipment, the first document that must be obtained a

A

permit

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5
Q

The primary and secondary winding of a transformer:

are wired in series

are wired in parallel

are not physical connected

none of the above

A

are not physically connected

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6
Q

A current larger than normal, but flowing outside its normal current path is referred to as:

overload

over current

short circuit

ground fault

A

short circuit

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7
Q

A standard Code fuse will have an interrupting capacity of ___________amps.

10,000

100,000

200,000

none of the above

A

10,000

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8
Q

Thermal overload protection:

aids motor warm up

prevents motor from freezing

protects motor and conductors from mechanical damage

provides electrical protection of motors

A

protects motor and conductors from mechanical damage

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9
Q

An overcurrent is

a current above normal

a current shorted to ground

a short circuit

all of the above

A

a current above normal

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10
Q

A dual voltage delta connected three phase motor will have how many leads located in terminal box?
Question 20 options:

6

9

15

3

A

9

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11
Q

A current larger than normal, but flowing within its normal current path is referred to as an:
Question 23 options:

overload

recurrent

short circuit

ground fault

A

overload

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12
Q

In a pure inductive load circuit how many electrical degrees out of phase is the current with the voltage
Question 24 options:

90

270

160

30

A

90

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13
Q

The current the motor will draw at start-up is known as the:
Question 25 options:

full load amperage

rated load amperage

running load amperage

locked rotor amperage

A

locked rotor amperage

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14
Q

The primary and secondary winding of an auto transformer:
Question 26 options:

are wired in series

are wired in parallel

are not electrically connected

none of the above

A

are wired in parallel

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15
Q

The maximum current rating of a plug fuse is________amps.
Question 27 options:

25

30

40

15

A

30a

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16
Q

Which type of circuit breaker provides for both overload and short circuit protection:
Question 28 options:

thermal

magnetic

thermal-magnetic

any of the above

A

thermal-magnetic

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17
Q

In electrical circuits where devices are wired in parallel:
Question 29 options:

the total voltage is applied to each device

the total current flows through each device

the total resistance is the sum of all the resistors

all of the above

A

all of the above

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18
Q

What is the purpose of the normally open contact wired in parallel with the start button , in a push start and stop button ?
Question 30 options:

To restart the system once it has stopped.

It is used as a holding circuit as the start button is released.

There is no normally open contact in parallel with the start button.

To deenergize the coil in order to get the circuit restarted.

A

it is used as a holding circuit

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19
Q

A series circuit consists of three resistor. If one resistor is removed, and the remaining resistors are connected in series to the same source, then the current in each of these two resistors will be:
Question 32 options:

increased

decreased

the same as before

zero

A

increased

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20
Q

The amount by which the current leads or lags the voltage in an alternating current circuit is known as:
Question 33 options:

phase angle

induction angle

starting current

running current

A

phase angle

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21
Q

The term “slip” is______________________________________.
Question 34 options:

the amount of horse power available due to motor resistance

the difference between the motor full operational rpm rating and the speed of the rotating magnetic field.

the difference in motor rpm between the time the start winding circuit is opened and when the motor reaches full speed

the difference between the motor full operational rpm rating and the actual speed under load.

A

the difference between the motor full operational rpm rating and the actual speed under load

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22
Q

The normally open contact on a defrost timer is wired in series with the …..
Question 35 options:

Motor timer circuit.

Defrost heaters.

Cooling cycle.

There is no normally open contact on a defrost timer.

A

defrost heaters

23
Q

If an open occurs in one branch of a parallel circuit, the line current (total current) will:
Question 38 options:

increase and the total circuit resistance will decrease

decrease and the total circuit resistance will increase

decrease and the total circuit resistance will decrease

be zero and the total circuit resistance will infinity

A

decrease and total circuit resistance will increase

24
Q

Typical insulators are:
Question 39 options:

copper, silver, gold

brass, bronze, steel

glass, rubber, plastic

aluminum, nickel, magnesium

A

glass, rubber, plastic

25
Q

IF fuses are used for overload protection, how many fuses are required for a 230 volts single phase compressor motor

A

2

26
Q 
Overload protection (fuse) for a hermetic motor compressor must not exceed \_\_\_\_\_\_ of FLA.
Question 42 options:

120%

125%

115%

140%

A

125%

27
Q

If a conductor carrying alternating current is formed into a coil, the magnetic field will:
Question 43 options:

be decreased

be increased

remain the same

be increased by 10 times

A

be increased

28
Q

How would switches used as safety devices be connected with respect to the load they are protecting.
Question 44 options:

in series

in parallel

in series parallel

makes no difference

A

in series

29
Q

The voltage rating of a conductor is determined by:
Question 45 options:

the size of the conductor

the type of insulation around the conductor

the application of the conductor

there is no voltage rating on conductors

A

type of insulation around the conductor

30
Q

How much current would a 200 watt light bulb draw from a 120 volt source:
Question 46 options:

  1. 76 amps
  2. 67 amps
  3. 76 amps
  4. 67 amps
A

1.67a

I = W/E

31
Q

What is the major difference between a contactor and a relay ?
Question 47 options:

The amount of current it can carry.

The amount of voltage flowing through it.

It is wired differently in a circuit.

The coil of a relay is wired in series with the start winding .

A

the amount of current it can carry

32
Q

A coil of wire carrying alternating current produces a type of resistance known as:
Question 49 options:

capacitive reactance

capacitive inductance

inductive reactance

impedance

A

inductive reactance

33
Q

In an AC resistive load circuit the current wave will always be in phase with the voltage wave and considered to have a power factor of 1.
Question 50 options:
True
False

A

true

34
Q

The voltage rating of a fuse must be equal to or greater than the applied voltage of the circuit it is protecting.
Question 51 options:
True
False

A

true

35
Q

As the current in a conductor decreases the magnetic lines of flux surrounding the conductor collapse inward.
Question 52 options:
True
False

A

true

36
Q

The holding coil on a motor starter or contactor will always be the same voltage as the load circuit.
Question 54 options:
True
False

A

false

37
Q

The locked rotor amperage of a motor is approximately 6 times that of the full load amperage.
Question 56 options:
True
False

A

true

38
Q

The correct colour coding for single phase grounded 120 volt circuit would be black for line conductor, neutral, and a green or uninsulated ground.

     True
     False
A

true

39
Q

As the current in a conductor is increased, the magnetic lines of force around the conductor also increase in concentration and in number.
Question 59 options:
True
False

A

true

40
Q

A motor disconnect switch may be fused or unfused and are rated for voltage, and amperage according to the load of the circuit.
Question 60 options:
True
False

A

true

41
Q

The most common starting device used on a PSC motor is the current relay or electronic.

true
false

A

false

42
Q

Increasing the number of turns an electromagnet has, will increase the strength of the electromagnetic field.
Question 63 options:
True
False

A

true

43
Q

A thermal type circuit breaker can be used if instantaneous response is required to overcurrents.
Question 65 options:
True
False

A

false

44
Q

A motor disconnect for an outdoor condensing unit where the actual switch is located outdoors requires a watertight enclosure (NEMA 4) or (NEMA 3).
Question 66 options:
True
False

A

true

45
Q

Another name for magnetic lines of force is magnetic flux.
Question 68 options:
True
False

A

true

46
Q

The magnetism in an electromagnet is just as strong when the electrical current is not flowing as it is when the current is flowing.
Question 70 options:
True
False

A

false

47
Q

On single phase 3 wire circuits the correct conductor color coding would be red and black for line conductors and white for neutral.
Question 71 options:
True
False

A

true

48
Q

Magnetic lines of force start at the north pole and end at the south pole.
Question 72 options:
True
False

A

true

49
Q

Impedance is the electrical term used to measure the total opposition to current flow in an AC circuit.
Question 73 options:
True
False

A

true

50
Q

Cartridge type fuses come in single element form only.
Question 74 options:
True
False

A

false

51
Q

Cartridge type fuses come in single element form only.
Question 74 options:
True
False

A

false

52
Q

Contactors and relays are very similar as per their application and normally you will find relays used when the current draw of the controlled load is less than 20 amps.
Question 75 options:
True
False

A

true

53
Q

Two resistors are connected in series to a 12 volt battery. One resistor is 4 ohms and the other resistor is 8 ohms. the voltage drop across the 4 ohm resistor would be:
Question 13 options:

zero volts

less then the voltage drop across the 8 ohm resistor

more than the voltage drop across the 8 ohm resistor

the same as the voltage drop across the 8 ohm resistor

A

less then the voltage drop across the 8 ohm resistor

Single-Phase, Three-phase, Circuit Protection (6 decks)

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