HVAC Flashcards
What type of charge does an electron have? A. positive B. Negeative C. Neutral D. Negative- positive
B
If five electrons combine with three protons, the net charge will be A. negative B. positive C. zero D. neutral
A
what part of an atom moves from one atom to another? A. proton B. Neutron C. electron D. molecule
C
Typical insulations are A. copper, silver, gold B. steel, bronze, brass C. glass, rubber, plastic D. aluminum, nickel, magnesium
C
The ampere is
A. the difference in potential between two charges
B. a measure of the quantity of electrons flowing past a point in the ectrical circuit in a given time
C. the unit of measure for resistance
D. the unit of measure for capacitance
B
If two light bulbs are wired in series and one bulb burns out, the other bulb will A. go out B. stay on C. stay on, but it will be dimmer D. stay on, but it will be brighter
A
what happens to the currnt in a circuit if the resistance is increased A. the current remains the same B . the current increases C. the current decreases D. this cannot be determined
c
what happens to the currnt in a circuit if the resistance is increased A. the current remains the same B . the current increases C. the current decreases D. this cannot be determined
c
An element in an electric heating unit is connected to a 232-V power supply. The current flow through the element is 19 A. What is the resistance of the element? A. 8 B.10 C.12 D.14
c
As loads are added ina parrallel circuit, the total resistance of the circuit. A. will increase B. will decrease C. will remain the same D. cannot be determined
B
To find the watts of electrical power in an electrical ciriuit, you multiply \_\_\_\_\_ together. A. ohms and amperes B. ohms and volts C. volts and amperes D. volts, amperes, and ohms
C
If a conductor carrying electrical current is formed into a coil, the magnetic field around the wire will. A. cancel out B. increase C. decrease D. remain the same
B
T/F Ohmmeters are to be used only on circuits that are de-energized.
T
T/F In a circuit with two or more ressistance in series, the total resistance in the circuit is the sum of the resistance.
T
T/F IF three bulbs are wired in parrallel and one bulb burns out, the total current of the circuit will decrease.
T
T/F In a circuit with two or more resistance in parallel, the total resistance in the circuit is the sum of the resistance in the circuit.
F
T/F When calculating the total resistance of a parallel circuit, the result will always be lower than the lowest resistance.
T
T/F One kilowatt of electrical energy is equal to 1,000,000 watts.
F
T/F IF a conductor carrying electrical current is formed into a coil, the strength of the magnetic field generated by the wire wil increase.
T
T/F The unit of measurement for the charge a capacitor can store is called a Joule.
F
T/ F As the diameter of a wire increases, its resistance will also increase.
F
T/F Copper wire size are measured in circular mills.
T
T/F The main purpose of a rectifier is to convert direct current (DC) to alternating current (AC).
F
T/F A PTC thermistor causes the resistance of the thermistor to increase when its temperture rises.
T
T/F A single diode can be connected as a full wave rectifier.
F
T/F When checking a diode with an ohmmneter and the meter shows a resistance, if the merer leads are reversed, it should show infinity.
T
T/F A heat sink is a device to improve the purity of the electrons in an electrical circuit.
F
A good conductor of electricty has few ___________ electrons, which cna move easily from one atom to another.
Valence
The unit of meausure for the current flow of electrical energery is the
__________.
Ampere
The unit of measure for the electrical pressure forcing electrical energy through a conductor is the __________.
volts
_____________ are used to measure the intensity of current flow in a circuit or a particalar brach in a circuit, so they are wired in series with the circuit being evaluated.
Ammeres
The unit of measure for resistance is the ________.
ohms
If there was a current flow of 6 A in a 120 V circuit, the resistance of thee circuit would be _______ ohms.
20
A transformer has 10,000 turns of wire in the secondary and 100 turns in the primary. The transformer is connected to a line voltage of 120 V. The output voltage will be ________ volts.
12,000
A solid state device that allows electrical energy to flow through in only one direction is called ________.
rectifer or diode
The automatic control of a system is inteneded to
A. maintain the working conditions of the equipment with a controllable device
B. evalute overloading situations
C. maintain stable or constant condtions without excessive human interference
D. maintain safe operations for service technicatians
C
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
C
When a control is required to control space or product temperture, it is called a A. safety device B. thermostat C. pressure control D. speed control
B
A thermal system overload may occur if a specific electriacl or mechanical component is not cooled properly, resulting in A. underload B. failure C. stagnation pressure D. overheating
D
Devices, such as thermoostats, that open and close their contacts during the \_\_\_\_\_ operation of the system are refferred to as operational controls. A. Normal B. Initial C. Most recent D. Final
A
THe compressor in the refregerator has a protective device that keeps it from overloading and damaging itself. This device is called a A. overload B. capacitor C. mass control D. speed control
A
The metals most often used in a bimetal temperture controls are A. copper and brass B. copper and steel C. brass and steel D. brass and aluminum
C
An example of a bimetal device is a A. snap-disc B. mercury-filled tube and diaphragm C. thermistor D. bordom tube
A
The bourdom tube
A. strightens out with an increase in voltage
B. curls inward with an increase in vapor pressure
C. strighterns out with an increase in electrical current
D. strighten out with an increase in vapor pressure
D
A thermocouple is a device that A. converts heat to mechanicla movement B. converts heat to fluid flow C. converts heat to electrical energy D. couples two temperture controls together
C
T/F Brass and steel have a different rate of expanstion and contraction when heated or cooled.
T
T/F Fluid expansion is a way to sinse temperture change.
T
T/F Bellows are normally used with a vapor instead of a liquid inside it.
T
T/F A properly operating thermocouple connected to a solenoid in a gas valve should put out 20 to 30 millivolts.
T
T/F A thermistor is a device that producesa voltage across the hot and cold juctions when heated.
F
The most popular typw of element used for a temperature control of a gas hot water heater is rod and _________.
Tube
Thin metal mebrane that can operate controls based on the pressure exerted on it
diaphragm
Based on the concept that different metals will react differently to heat causing currnet to flow
thermocouple
Bimetal device used to sense water heater temperatures
rod and tube
A higher output thermocouple
thermopile
Device whose resistance changes with respect to temperture, used to control electronic circuits
thermistor
Two unlike metaals conncted back to back
bimetal strip
The purpose of a heat anticipator is to
A. anticipate a sudden rise in temperture
B. keep the thermostat warm
C. reduce the temperture swing of a conditioned space
D. ensure that the system transformer does not overload
C
The difference between system overshoot and system lag is called A. room temperture B. temperature rise C. temperature swing D. room swing
C
What is meant by the term “detent”?
A. slow motion of a contact to ensure electrical contact
B. rapid making and breaking of a contact
C. the compenation furnished by heaters in the thermostat
D. the control of the blower in the air handler
B
The heat anticipator in the thermmostat control circuits in the hrating mode is active when the A. heating contact is open B. heating resistor is closed C. fan switch is open D. fan swich is closed
B
The heater in the thermostat control circuit in the cooling mode is active when the A. cooling contact is open B. cooling contat is closed C. fan switch is open D. fan swich is closed
A
To properly set the heat anticipator, the \_\_\_\_ must determine what the cuurent flow is through the heating control circuit when the furnace is operating in a steady state condition. A. manufacturer B. homeowner C. electrician D. heating technication
D
The cold anticipator is wired in \_\_\_\_\_\_ with the mercury bulb cooling contacts and is energized during the off cycle. A. parallel B. series C. sequence D. oppostion
A
Line voltage thermostats habe heavier contacts and use which type of sensing element A. bimetal B. bellow C. remote bulb D. all of the above
D
To obtain an accurate reading of a fluid in a large pipe, a technican should
A. strap a dial-type pocket thermometer to the pipe
B. ise a digital thermometer in a glass of ice water
C. use a permanenty mounted thermometer in a well
D. any of the above will work fine
c
Al low pressure control has a high event and differential setting. The technician wants the system to turn on at 28 psig and shut down at 2 psig. What would be the proper settings?
A. high event: 28 psig, differential: 2 psig
B. high event: 2 psig, differential: 2 psig
C. high event: 28 psig, differential: 26 psig
D. high event: 2 psig, differential: 28 psig
C
If the suction pressure of a system is 60 psig and the oil pump is 85 psig, what is the net oil pressure? A. 60 psig B. 25 psig C. 85 psig. D. 145 psig
B
Oil pressure safty controls measure the difference in pressure to establish
A. the compressor is running
B. the oil pump is runing
C. that negative oil pressure is present
D. that posistive oil pressure is present
D
To prove that the combustion blower motor is operating before igntion, a \_\_\_ would be used. A. toggle switch B. pressure differential C. push button switch D. sail switch
B or D
To control ice build-up on a heat pump outdoor coil in the heating cycle , a \_\_\_\_ is attached to a large diaphragm. A. toggle switch B. micro- switch C. push button switch D. sail switch
B
Where would a water regulating valve that is controlling head pressure be installed?
A. water circuit at inlet of condenser
B. discharge line at outlet of compreesor
C. suction line
D. liquid line close to the condenser
A
When a water regulating valve is used to control the head pressure of a water-cooled system, the valve's spring is acting againsr which pressure to modulate the water flow? A. head pressure of the system B. water pressure C. suction pressure D. atmospheric pressure
A
T/F The heat antipipator in a thermostat prevents the temperture in the conditioned space from rising above the thermostat setting.
T
T/F The cold anticipator stars the cooling system early to allow the air-conditoned system to get up to capacity when needed.
T
T/F The advantage of using a thermistor-type thermometer over mercury-filled thermometer for measring refrigerant line temperture is that the themistor-type does not have to be insulated.
F
T/F A helix coil is used in some applications to sense temperture in a moving air stream.
T
T/F A dual pressure control is actually a low pressure control and high pressure control connected in parallel with each other.
F
T/F Many natural gas fired heating units operate at a maniflod pressure of 3.5 in W.C
T
A control can be which of the following? A. electrical B. mechanical C. electrical and mechanical D. all the above
D
An example of a power consuming device would be a _______ while an example of a non-consuming device would be a
A. single-pole single-throw switch, light bulb
B. light bulb, electric motor
C. electric motor, light bulb
D. light bulb, single throw single pole switch
D
An electrical power consuming component
A. is normally wired in series in an electriacal circiut
B. is normally used to pass power to another component
C. is often a basic switch
D. is also known as a load
D
The line side of a switch is the A. side the load is connected to B. neutral side of the circuit C. side the power source is connected to D. side with the white wire
C
If an air conditioning system is calling and the compressor is running but the indoor ( evaporator) fan is not running, which terminal on the thermostat will the technician most likely check first? A. G B.R C.Y D.W
A
The \_\_\_\_\_\_ is nothing more than a set of switches. A. transformer B. coil C. motor. D. thermostat
D
The continuity through a heat relay is checked used a A. ohmmeter B. voltmeter C. clamp-on ammeter D. micron gauge
A
A 10-wrap amoerage multiplier is used with an A. voltmeter B. clamp-on ammeter C. ohmmeter D. megger
B
Transformers are rated using A. volt-amperes B. volt-ohms C. amperes-ohms D. volt-resistance
A
A \_\_\_\_\_ is the easiest diagram to use to follow a circuit. This diagram normally can be studied briefly, and the circuit function should become obvious. A. pictorial diagram B. ladder diagram C. layout D. oblique drawing
B
AN electrical diagram showing the approximate location of the components is called a A. pictrial diagram B. ladder diagram C. layout D. oblique drawing
A
T/F If line one of a circuit had a potential of 120 V and line two was neutral, the potential voltage (difference) between line one and two would be zero volts.
F
T/F The heat anticipator in a thermostat is usually an adjustable type.
T
T/F The cooling anticipator in a thermostat is usually an adjustable type.
F
T/F When checking thermostat circuits, an insulted jumper wire is a handy tool.
T
T/F When conditions are correct, the rheostat will pass power through the device onto the system components to be controlled.
F
T/F While troubleshooting a 24 V control circuit consisting of a thermostat, a pressure control, and a contactor coil, the technicain reads 24 V across the thermostat, 0 V across the pressure control, and 0 volts across the contactor coil. The technician makes the follwing statement. The following statements are all considered to be true.
A. the transformer is burned out
B. the thermostat is open
C. the contactor coil is energized
F
T/F A 120-V/24-V control tansformer has a VA rating of 20. The maximum amperage the transformer will put out is 0.8 amps.
T
T/F When using a ten-wrap multiplier, the reading on the meter must be multiplied by ten.
F
How is the cooling anticipator normally wired to the cooling contacts?
parallel
How is the heat anticipator normally wired to the hrating contacts?
series
In a residentail air conditioning system, how are the outdoor fan and compressor wired with respect to each other?
parellel
In a high voltage circuit, if the fan motor a power-passing or power- consuming device?
Power-consuming
