Unit 12 Test Flashcards
What is a device that opens or closes a set of contacts when its coil is energized, which usually carries less than 20 amperes?
Relay
What is a device that decreases the input voltage?
Transformer
What is a schematic that cross references the components and their lettered designations?
Legend
What is the simplest type of overload?
Overload (thermal)
What type of system heats a conditioned space by reversing the refrigeration cycle?
Heat Pump
Devices such as motors, solenoids, heaters, and signal lights are called what?
Load
What is the device called that breaks the circuit when a high current draw exists?
Fuse
What kind of device is used to rotate a compressor?
Motor
What’s the type of electrical device that opens or closes to control a load?
Switch
What are the two types of contact?
Normally Open and Normally Closed (might be poles)
What do we call a contactor with a means of overload protection?
Magnetic Starter
What’s another name for a line or label diagram?
Pictorial Schematic
What is the position of an electrical device that is open when the device is de-energized?
Normally Open
What do we call a device that responds to a temperature change by opening and closing a set of contacts?
Thermostat
What is the term used to describe the number of positions of a set of movable contacts?
Throw
What’s the name of a wiring diagram that is laid out in a circuit-by-circuit arrangement?
Schematic Diagram
What do we call the position of an electrical device that is closed when it’s de-energized?
Normally Closed
What do we call a device that opens and closes a set of contacts, and it’s capable of carrying loads in excess of 20 amperes?
Contactor
What do we call it when we supply electrical energy?
Energized
What’s the device that breaks the control circuit during a motor overload?
Pilot Duty
What do we call the material that retards the flow of electrons?
Insulator
What do you set your meter to be able to read resistance?
Ohms (Ω)
Resistance is the term used to describe the opposition to electron flow. (True or False)
True
When current is flowing through a conductor, amperage is produced around the conductor. (True or False)
False
When checking the amperes of a circuit, the ammeter should be clamped around two wires in the circuit. (True or False)
False
If a single conductor of a circuit is wrapped around the jaws of a clamp ammeter six times and the reading is 24 amps, what is the true amp reading?
4 Amps
A complete circuit, with no open switches or broken wires, is said to have what?
Continuity
Voltage is equal to amperage times resistance. (True or False)
True
The amperage draw of a series circuit is equal to the voltage divided by the total resistance. (True or False)
True
What is the resistance reading of a good motor winding?
Low (typically near 0 ohms)
If you’re reading infinity on your ohmmeter when checking a motor winding for resistance, it indicates the winding is what?
Open
Given a 115-volt and 25-amp series circuit with three resistance values (R1 is 100 Ohms, R2 is 160 Ohms, and R3 is 200 Ohms), what is the total voltage drop throughout the circuit?
115 Volts
(Series circuit, the voltage drop equals the source of voltage)
Given a 115-volt and 25-amp series circuit with three resistance values (R1 is 100 Ohms, R2 is 160 Ohms, and R3 is 200 Ohms), what is the total resistance of the circuit?
460 Ohms
(Series circuit, total resistance equals the sum of individual resistances: R1 + R2 + R3 = Total)
If we had a 440-volt parallel circuit with two resistance values (R1 is 220 ohms, and R2 is 220 ohms), what is the total amp draw of that circuit?
4 Amps
(Parallel circuit, 1/R total = 1/R1 + 1/R2);
I = V/R)
If we had a 440-volt parallel circuit with two resistance values (R1 is 220 ohms, and R2 is 220 ohms), what is the total resistance of that circuit?
110 Ohms
(1/R Total = 1/R1 + 1/R2)
In HVAC systems, the common low-voltage wire colors are typically as follows:
• Red (R):
Power (24V AC)
In HVAC systems, the common low-voltage wire colors are typically as follows:
• White (W):
Heating
In HVAC systems, the common low-voltage wire colors are typically as follows:
• Yellow (Y):
Cooling(Thermostat/contactor)
In HVAC systems, the common low-voltage wire colors are typically as follows:
• Green (G):
Fan
In HVAC systems, the common low-voltage wire colors are typically as follows:
• Blue (C):
Common
In HVAC systems, the common low-voltage wire colors are typically as follows:
• Orange (O):
Heat Pump
