Electric Midterm

Question 1

What is the best type of push-button operator to use in an emergency stop application?

Answer 1

Jumbo Mushroom

Question 2

A selector switch with a legend plate labeled SLOW/FAST is an example of what type of selector switch?

Answer 2

2 Position

Question 3

A selector switch with a legend plate labeled SLOW/OFF/FAST is an example of what type of selector switch?

Answer 3

3 Position

Question 4

In a truth table, X represents what contact condition?

Answer 4

Closed Contact

Question 5

In a truth table, O represents what contact condition?

Answer 5

Open Contact

Question 6

What is the main advantage of using a joystick in an application such as moving the passenger loading ramp for an airplane?

Answer 6

Control many operations without removing hand

Question 7

In a joystick symbol, what does the dot denote?

Answer 7

Position needed to actuate

Question 8

If the moving part of a limit switch is drawn below the contacts in the symbol, is the switch NO/NO held closed or NC/NC held open?

Answer 8

NO/NO held closed

Question 9

If the moving part of a limit switch is drawn above the contacts in the symbol, is the switch NO/NO held closed or NC/NC held open?

Answer 9

NC/NC Held Open

Question 10

What type of limit switch actuator allows detection of a moving object from any direction except head on?

Answer 10

Wobble Stick

Question 11

What type of limit switch actuator allows the arm length to be adjusted to meet the application?

Answer 11

Lever Arm

Question 12

When a foot switch has 3 positions, does the toe operate all 3?

Answer 12

No

Question 13

Is the OFF position of a foot switch usually a maintained position or a spring loaded position

Answer 13

Spring Loaded

Question 14

What does a pressure switch rated in inches of W.C. refer to?

Answer 14

Inches of Water Column

Question 15

If a pressure switch is used to maintain a set pressure, are NO or NC contacts used to control the compressor motor starter?

Answer 15

NC

Question 16

If a temperature switch is used in a heating system to maintain a set temperature, are NO or NC contacts used to control the heating contactor?

Answer 16

NC

Question 17

If a temperature switch is used in a cooling system to maintain a set temperature, are NO or NC contacts used to control the cooling contactor?

Answer 17

NO

Question 18

If a flow switch is used to sound an alarm when there is no flow, are NO or NC contacts used to control the alarm?

Answer 18

NC

Question 19

If a flow switch is used to detect flow in an automatic sprinkler system that had detected a fire and opened the sprinklers to flow, are NO or NC contacts used to control the alarm?

Answer 19

NO

Question 20

If a level switch is used in a charging system, are NO or NC contacts used to control the pump motor starter?

Answer 20

NC

Question 21

If a level switch is used in a disharging system, are NO or NC contacts used to control the pump motor starter?

Answer 21

NO

Question 22

Is a diode used to help protect electrical contacts in an AC or DC load switching circuit?

Answer 22

DC

Question 23

What position are most flow switches designed to operate in?

Answer 23

Horizontal

Question 24

If voltage is measure on the incoming side of a switch, but not on the outgoing side, what is the state of the switch?

Answer 24

It is open

Question 25

If voltage is measured on both sides of a switch, what state is the switch in?

Answer 25

Closed

Question 26

What do most flow switches use?

Answer 26

A paddle

Question 27

What does CEMF stand for?

Answer 27

Counter Electro-Motive Force

Question 28

Can 1 push-button operate both NO and NC contacts?

Answer 28

Yes

Question 29

What are the two windings of a transformer called?

Answer 29

Primary and Secondary

Question 30

If a transformer has a turns ratio of 1:4, what is the voltage ratio?

Answer 30

1:4

Question 31

If a transformer has a turns ratio of 1:4, what is the current ratio?

Answer 31

4:1

Question 32

If a transformer has a turns ratio of 1:4, what is the power ratio?

Answer 32

1:1

Question 33

If a transformer has a turns ratio of 1:4 and 115V is applied to the primary, how many volts are on the secondary?

Answer 33

460V (115x4)

Question 34

Why are transformer iron cores laminated?

Answer 34

Minimize Eddy Current Losses, which produce heat

Question 35

What type of electrical service is most common for residential dwellings?

Answer 35

120V/240V single phase

Question 36

Why do control transformers usually have two primary coils?

Answer 36

So you can use different voltages (Tyically 240V or 480V)

Question 37

What do "X" markings on a transformer represent?

Answer 37

Lower Voltage

Question 38

What do "H" markings on a transformer represent?

Answer 38

High Voltage

Question 39

When connecting the primary of a control transformer to high voltage, are the coils connected in series or parallel?

Answer 39

Series

Question 40

When connecting the primary of a control transformer to low voltage, are the coils connected in series or parallel?

Answer 40

Parallel

Question 41

Is a transformer's VA rating based on the primary ot secondary of a the transformer?

Answer 41

Secondary

Question 42

What information is needed to size a transformer?

Answer 42

•Input Voltage Available •Output Voltage Desired •Output Current Required

Question 43

Can you use a transformer for DC voltage?

Answer 43

No