electrical
In the schematic what voltage is found from terminal G to the load side of the transformer
0 volts
What voltage is found across a fuse in line 10 when its energized
0 volts
What voltage is found across contacts in line 8 when energized
0 volts
What is the synchronous speed for a 4 pole 60 hz motor
1,800 rpm
Relays are generally used to control inductive loads up to how many amps
10 amps
3 300 ohm resistors are wired in parallel. What is the total resistance
100 ohms
2.1 kilowatts equals how many watts
2,100 watts
3 defrost heaters, each rated at 15 ohms are wired in parallel with 120 volts. what is total power
2,880 watts
In a 240 volt 3 phase motor what voltage is found between l1 and l2
240 volts
What voltage is found across a condenser fan motor in a 240 volt system
240 volts
What resistance must be placed in a 120 volt circuit to limit current to 2 amps
60 ohms
If a transformer has 1,000 turns on the primary and 500 on the secondary, what is the secondary voltage if 120 volts are applied
60 volts
Which of the following is an acceptable temporary replacement for a run capacitor rated at 35 microfarads, 440 VAC
A capacitor rated at 40 microfarads, 440 VAC
Excessive current can be caused by what
A short circuit
When thermostat contacts are closed the compressor and condenser fan motor are not running, but the blower motor is running. What can cause this
An open high pressure, low pressure switch, overload, or oil pressure switch
Which diagram represents a pressure switch that opens on pressure rise
C
A diode is used to do what
Control the direction of electron flow
Digital direct controls are used for what
Equipment operation and monitoring
In the schematic, the coil on line 12 controls what
The blower motor relay
which statement about current is true
current increases when voltage increases
When checking the windings of a 3 phase motor what should the resistance readings be
equal across all terminals
capacitor start capacitor run motors provide what benefits
high starting and running torque
capacitors are connected in what configuration with the start winding
in series
What is a device with overload protection used to control a motor called
line starter
What does a meter read when testing a capacitor with an ohmmeter
low resistance, then return to high reading
electronically commutated motors are designed to do what
maintain a constant velocity
Thermal overload contacts on a line starter are typically what type
manual reset
The electron has what type of charge
negative charge
Which meter is used to bench check a motor for shorts or open windings?
ohmmeter
What formula determines electrical power in a circuit
power=voltage x current E x I
The most common type of transducer in HVAC systems is based on what
pressure transducer
like charges do what
repel each other
What happens to resistance in a positive temperature coefficient thermistor as temperature increases
resistance increases
What material is best suited for use in semiconductors
silicon
A thermocouple generates what type of current
small dc current
Current flow is defined as
the flow of electrons in a circuit
What connects to terminals T1, T2, T3 on a motor starter
the load
the speed of a single phase motor is determined by what
the number of stator poles
In a series circuit what do the voltage drops across each resistance add up to
the total source voltage
how is a capacitor used discharged before testing
using a resistor
Transformers are rated according to what
volt amps VA
fuses are sized based on what
voltage and amperage
voltage can be calculated using what formula
voltage=current x resistance I x R ohm's law
the electric meter on a house measures
watts
What is the symbol for impedance in an ac circuit
z
