Electrical Student Outcome Assesment HVAC

In the schematic, what voltage would be found across the fuse in line #10?

0 volts

In the schematic, what voltage would be found from terminal R to terminal G on the thermostat?

0 volts

In the schematic, what voltage would be found from terminal Y to the input side of the coil on line #11?

0 volts

Which of the following is equal to 100 milliamps?

0.10 amperes

Relays used in the HVAC industry are generally used to control loads up to _____ amps

10

Three 300 ohm resistors are wired in parallel. The total resistance equals?

100 ohms

The synchronous speed of a four pole, 60 Hz single phase motor is;

1800 rpm

Which of the following is equal to 2.1 KV?

2,100 volts

How many watts of power are used by a heater operating at 460 volts and drawing 5 amps?

2300 watts

In the schematic, what voltage would be found from terminal Y to the output side of the coil on line #11?

24 volts

A transformer has 1000 turns of wire in the primary coil and 2000 turns in the secondary coil. If 120 volts are applied, the output voltage will be....

240 volts

In the schematic, what voltage would be found across the contacts in line #8?

240 volts

In the schematic, what voltage would be found across the transformer primary?

240 volts

Utility companies usually supply residential homes with__________service.

240V, single phase, three wire

Three resistors are wired in parallel. Two of the resistors have a value of 12 ohms, one resistor has a value of 6 ohms. What is the total resistance of the circuit?

3 ohms

What is generally considered to be the maximum allowable (plus or minus) supply voltage variation?

5%

How much resistance must be placed in a 110 volt circuit in order to limit the current to 2 amps?

55 ohms

A parallel circuit contains an 18 ohm and a 9 ohm resistor. The total resistance equals.....

6 ohms

A parallel circuit consists of three resistors. R1 = 30 ohms R2 = 15 ohms R3 = 10 ohms If the current through R2 = 4 amperes, what is the source voltage?

60 volts

A transformer has 1000 turns of wire in the primary coil and 500 turns in the secondary coil. If 120 volts are applied, the output voltage will be......

60 volts

One horsepower is equal to______watts?

746

Three resistors are wired in series. Each has a value of 300 ohms. What is the total resistance of the circuit?

900 ohms

Any material that will readily release electrons is called....

A conductor

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan motors are short cycling. The blower motor is not running. When the fan switch at the thermostat is moved from the AUTO position to the FAN ON position, the blower runs. This could be caused by;

A faulty thermostat-AUTO/FAN ON switch

When checking the windings of a three phase motor?

All three terminals should show the same resistance.

How are fuses sized?

Amps and Volts

In the schematic, the coil on line #12 controls;

Blower motor relay

When testing the windings of a single-phase motor, technician #1 says that the common and run terminals show the lowest resistance. Technician #2 says that the pair of terminals with the highest resistance will indicate that the other terminal is the common. Who is correct?

Both technicians #1 and #2

A________ may be used on a single-phase induction motor to disconnect the start winding after the motor starts.

Centrifugal switch, Amperage relay, Potential relay (any of the above)

Which of the following statements about current is true?

Current flow will increase when voltage increases

Resistance can be calculated by

E divided by I

If contacts become dirty or pitted, it is acceptable to sand or file them as a permanent repair.

False

Single phase motors are more efficient than three phase motors

False

When testing a motor with an ohmmeter, one winding shows a 1000 ohm continuity to the motor frame. This is an indication of a good safety ground.

False

With a motor running at full load, voltmeter leads are placed on each side of the relay contacts. The voltmeter gives no measurable voltage. This is an indication of;

Good clean contacts

The safety ground conductor is usually color coded.....

Green

Electricity can produce...

Heat, light, magnetism (all of the above)

What would be the result of three defrost heaters, each 12.5 ohms. Wired in series to a 115 volt power supply, if the heaters were to supply a 360 watt heating load?

Heaters operate normally

The symbol for current is....

I

Voltage can be calculated by

I times R

240 volts

In the schematic, what voltage would be found across L1 to L2?

240 volts

In the schematic, what voltage would be found across the condenser fan motor?

If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called?

Inductive reactance

When current flows, a________________ is produced around the conductor.

Magnetic field

Capacitors are rated in....

Microfarads & Volts

Technician #1 says that an open transformer coil is indicated by a reading of 0 ohms on an ohmmeter. Technician #2 says that a shorted transformer coil is indicated by a reading of infinity on an ohmmeter. Who is correct?

Neither technician #1 nor #2.

Single phase motor speed is determined by the?

Number of stater poles.

What meter is used to bench check a motor for shorts or open windings?

Ohmmeter

What type of meter uses its own battery?

Ohmmeter

What is impedance?

Opposition to alternating current flow

A device used to control a motor is a

Relay, contactor, line starter (all of the above)

What is the term used to describe the output side of a transformer?

Secondary side

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan are not running. The blower motor is running. This could be caused by;

The HP, LP, overloads, or oil pressure switch are open (Line #11) and the contactor coil may be faulty (Line #11) ((Both A and B))

In the schematic, the coil on line #11 controls;

The compressor, condenser fan motor, and crankcase heater (all of the above)

Direction of rotation of a single phase induction motor is determined by?

The direction of current flow through the start winding.

What is current flow?

The flow of electrons in the circuit.

When resistors are wired in parallel....

The voltage drop across each resistor will be the same as the applied source voltage

A 240 volt, 3 wire circuit can be split into two 120 volt circuits.

True

A three phase system requires a minimum of three supply lines to the three phase load.

True

In the schematic, if the fuse in L2 is blown, the blower motor will continue to operate.

True

To discharge a capacitor prior to ohmmeter testing?

Use a 20,000 ohm resistor to short across the terminals

Transformers are rated according to;

VA at the secondary

Amperes can be calculated by;

W divided by E, E divided by R, and the square root of W divided by R. (All of the above)

Which of the following is the correct formula for determining wattage in an electrical circuit?

W= E times I

Thermal Overload

What is this symbol for?

Transformer

What is this symbol for?

pressure switch

What is this symbol for?

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan motors are short cycling. The blower motor is not running. This could be caused by;

a faulty blower motor or blower relay

An ohmmeter should never be connected to?

a live circuit

An electron has...

a negative charge

In a series circuit, the voltage drop across each resistance (load) will.......

always add up to equal the source voltage, depend on the value of each resistor, and depend on the current flow in the circuit. (All of the above)

The terminals T1, T2, and T3 are located at the_______of a contactor.

bottom

A capacitor opposes current flow in a circuit. This opposition is called....

capacitive reactance

To change direction of rotation of a three phase motor....

change the position of any two supply wires.

Contactors are rated according to the maximum amperage through the?

contacts

When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance will;

decrease

When testing a capacitor with an analog ohmmeter, the needle on the meter should;

deflect towards zero then return to infinite reading

A solenoid valve operates on the principle of.....

electromagnetism

A thermocouple can.....

generate a small electrical current, depending on temperature.

Overcurrent can be caused by

ground faults, overload, short circuit (all of the above)

Capacitors are always connected __________ to the start winding.

in series

When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance will;

increase

Impedance in a circuit is the result of....

inductive reactance, capacitive reactance, and pure resistance. (All of the above)

The total resistance of a parallel circuit will be.....

less than the smallest resistance

The thermal overload contacts on a line starter are usually________reset.

manual

Two 120 volt motors are wired in series, one is a 60 watt motor, the other is a 4 watt motor. The result would be;

neither motor would operate normally

What is resistance?

opposition to current flow

The_________drawing illustrates where the components are located on the appliance.

pictorial

A transducer can create a signal based on a form of energy such as.....

pressure

The capacitor start-capacitor run (CSCR) motor;

provides high starting torque and high running torque (Both A and B)

A capacitor analyzer is designed to....

read power factor percentage, diagnose an open or shorted, read the microfarad rating of a capacitor (all of the above)

Like charges will....

repel each other

In a single phase motor, which winding has the most resistance?

start

In electrical wiring, a black colored wire usually indicates;

the hot conductor

How many switches can be connected to a contactor coil control circuit?

unlimited

When replacing a capacitor;

use a replacement with the same value as the original, if a duplicate of the original is not available a capacitor that is up to !0% over capacity is ok, and never use a capacitor that is under capacity. (all of the above)

A step up transformer increases.....

voltage

The meter on a house measures the______passing through it.

wattage

In the schematic, the crankcase heater will operate;

when the compressor is off

Fuses are used to protect;

wires