Deck 13: Introduction to Automatic Controls

Question 1

Brass and steel have a different rate of expansion and contraction when heated or cooled .

Answer 1

True

Question 2

The compressor in the refrigerator has a protective device that keeps it from overloading and damaging itself. This device is called a(n)  ____.

A) overload
B) capacitor
C) mass control
D) speed control

Answer 2

A

Question 3

A thermal system overload may occur if a specific electrical or mechanical component is not cooled properly, resulting in ____.

A) underload
B) failure
C) stagnation pressure
D) overheating

Answer 3

D

Question 4

A properly operating thermocouple connected to a solenoid in a gas valve should put out 20 to 30 millivolts.

Question 5

A bellows is much like a(n) ____________________ ̶ it has a lot of internal volume and a lot of travel.

Question 6

The automatic control of a system is intended to ____.

A) maintain the working conditions of the equipment with a controllable device
B) evaluate overloading situations
C) maintain stable or constant conditions without excessive human interference
D) maintain safe operations for service technicians

Question 7

Modulating controls are used to ____.

A) start motors
B) stop motors
C) vary the speed of a motor
D) stop the flow of a liquid

Question 8

A common application for the rod and tube type of control is in a(n) ____________________-mounted limit control.

Question 9

Devices, such as thermostats, that open and close their contacts during the ____ operation of the system are referred to as operational controls .

A) normal
B) initial
C) most recent
D) final

Question 10

Adding length to a bimetal element is done by shaping the element. The shapes used are coiled, helix, hairpin, and ____________________.

Question 11

A thermistor is a device that produces a voltage across the hot and cold junctions when heated.

Question 12

An example of a bimetal device is a ____.

A) snap-disc
B) mercury-filled tube and diaphragm
C) thermistor
D) Bourdon tube

Question 13

When a control is required to control space or product temperature, it is called a ____.

A) safety device
B) thermostat
C) pressure control
D) speed control

Question 14

A thermocouple is a device that ____.

A) converts heat to mechanical movement
B) converts heat to fluid flow
C) converts heat to electrical energy
D) couples two temperature controls together

Question 15

The metals most often used in a bimetal temperature control are  ____.

A) copper and brass
B) copper and steel
C) brass and steel
D) brass and aluminum

Question 16

The most popular type of bimetal element used for temperature control of a gas hot water heater is rod and ____________________.

Question 17

The most common device used to sense change in temperature is called a(n) ____________________.

Question 18

Bellows are normally used with a vapor instead of a liquid inside it.

Question 19

Fluid expansion is a way to sense temperature change .

Question 20

The Bourdon tube ____.

A) straightens out with an increase in voltage
B) curls inward with an increase in vapor pressure
C) straightens out with an increase in electrical current
D) straightens out with an increase in vapor pressure

Question 21

Define "bimetal strip."

Question 22

Explain the difference between a Positive Temperature Coefficient (PTC) thermistor and a Negative Temperature Coefficient (NTC) thermistor.

Question 24

What is a thermopile?

Question 25

To make a bimetal element operate over a wide temperature range, what is done to the element?

Question 26

What is the major advantage of a remote bulb control?

Question 27

Define a diaphragm used in controls.

Question 28

How can pressure be used to control the temperature of a refrigerated space?

Question 29

Why are two different metals used to produce movement in bimetal elements?

Question 30

When referring to thermocouples, the hot  ____________________ is at a higher temperature level than the cold ____________________.