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Worksheets04. ACR-105 UNIT 13 END OF UNIT TEST
Total questions: 28
Worksheet time: 32mins
The automatic control of a system is intended to ____.
maintain the working conditions of the equipment with a controllable device
evaluate overloading situations
maintain stable or constant conditions without excessive human interference
maintain safe operations for service technicians
Modulating controls are used to ____.
start motors
stop motors
vary the speed of a motor
stop the flow of a liquid
When a control is required to control space or product temperature, it is called a ____.
safety device
thermostat
pressure control
speed control
A thermal system overload may occur if a specific electrical or mechanical component is not cooled properly, resulting in ____.
underload
failure
stagnation pressure
overheating
Devices, such as thermostats, that open and close their contacts during the ____ operation of the system are referred to as operational controls.
normal
initial
most recent
final
The compressor in the refrigerator has a protective device that keeps it from overloading and damaging itself. This device is called a(n) ____.
overload
capacitor
mass control
speed control
The metals most often used in a bimetal temperature control are ____.
copper and brass
copper and steel
brass and steel
brass and aluminum
An example of a bimetal device is a (a) .
The Bourdon tube ____.
straightens out with an increase in voltage
curls inward with an increase in vapor pressure
straightens out with an increase in electrical current
straightens out with an increase in vapor pressure
A thermocouple is a device that ____.
converts heat to mechanical movement
converts heat to fluid flow
converts heat to electrical energy
couples two temperature controls together
Brass and steel have a different rate of expansion and contraction when heated or cooled.
True
False
Fluid expansion is a way to sense temperature change.
True
False
Bellows are normally used with a vapor instead of a liquid inside it.
True
False
A properly operating thermocouple connected to a solenoid in a gas valve should put out 20 to 30 millivolts.
True
False
A thermistor is a device that produces a voltage across the hot and cold junctions when heated.
True
False
The most common device used to sense change in temperature is called a(n) .
Adding length to a bimetal element is done by shaping the element. The shapes used are coiled, helix, hairpin, and .
The most popular type of bimetal element used for temperature control of a gas hot water heater is rod and .
A common application for the rod and tube type of control is in a(n) -mounted limit control.
A bellows is much like a(n) —it has a lot of internal volume and a lot of travel.
When referring to thermocouples, the hot (a) is at a higher temperature level than the cold (b) .
What is a "bimetal strip"?
A strip made of two different metals bonded together that expand at different rates when heated
A single metal strip used in electrical circuits
A strip used for measuring temperature
A strip made of plastic and metal
Why are two different metals used to produce movement in bimetal elements?
To create a temperature differential
To generate electrical current
To cause bending due to different expansion rates
To improve conductivity
To make a bimetal element operate over a wide temperature range, what is done to the element?
It is coated with a special material.
It is made thicker.
It is made shorter.
the strip is lengthened.
What is a diaphragm used in controls?
A flexible membrane that responds to pressure changes
A rigid structure used for support
A type of electrical circuit
A component for data storage
What is the major advantage of a remote bulb control?
The control body can be located outside the controlled area for better access.
It is more energy efficient.
It is cheaper than traditional controls.
It has a longer lifespan.
What is the difference between a Positive Temperature Coefficient (PTC) thermistor and a Negative Temperature Coefficient (NTC) thermistor?
PTC thermistors increase resistance with temperature, while NTC thermistors decrease resistance with temperature.
PTC thermistors decrease resistance with temperature, while NTC thermistors increase resistance with temperature.
Both PTC and NTC thermistors increase resistance with temperature.
Both PTC and NTC thermistors decrease resistance with temperature.
What is a thermopile?
A group of thermocouples wired in series with each other to provide a higher output voltage.
A type of thermometer used for measuring high temperatures
A material that insulates against heat
A component used in refrigeration systems
