HVAC 202 Final Exam Study Guide Part 1
100 milliamps=
0.10 amps
Three 300 ohms resistors are wired in parallel. The total resistance equals ?
100 ohms
The voltage to ground of a "high Leg" or Stinger Leg" on a three phase open Delta System will be approximately
208
Which of the following is equal to 2.1KW?
2100 watts
How many watts of power are used by a heater operating at 460 volts and drawing 5 amps?
2300
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
Three defrost heaters, each 15 ohms are wired in parallel to a 120 volt power supply. How many watts of power will be used?
2880 Watts
Which of the following is generally considered to be within the maximum allowable (plus or minus) supply voltage variation?
5%
A parallel circuit contains a 18 ohm and a 9 ohm resistor. The total resistance equals?
6 ohms
How much resistance must be placed in a 120 volt circuit in order to limit the current to 2 amps?
60 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
1 horsepower =
746 watts
Any material that will readily release electrons is called
Conductor
The flow of electrons in the circuit
Current flow
Resistance can be calculated by
E/I
The safety ground conductor is usually colored coded
Green
The symbol for current is
I
Voltage can be calculated by
I x R
Opposition to alternating current flow
Impedance
Repel one another.
Like charges
Capacitors are rated in:
Microfarads and Volts
Which of the following meters must use its internal power to check a load or circuit?
Ohmmeter
Resistance is
Opposition to current flow
What is the term used to describe the output side of a transformer?
Secondary side
Which of the following materials would be best suited for use as a semi-conductor?
Silicon
Fuses are sized by
Volts and amps
What is the correct formula for wattage in an electrical circuit?
W= E times I
Which of the following is the symbol for Impedance in an AC circuit ?
Z
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;
add up to equal the source voltage
Two 120 volt incandescent light bulbs are wired in series, one is a 60 watt bulb, the other is a 4 watt bulb. The result would be:
both bulbs light
A diode is used to?
control the direction of electron flow
Which of the following statements about current is true?
current flow will increase when voltage increases
A _______is commonly used on a single phase fractional horse power compressor motor to disconnect the start winding after the motor starts.
current relay
Which of the following would be considered an inductive load?
electric motor
The capacitor start-capacitor run (CSCR) motor provides;
high starting torque and running torque
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
The total resistance of a parallel circuit will be
less than the smallest resistance
When current flows, a ____________ is produced around the conductor.
magnetic field
When testing a capacitor with an analog or digital ohmmeter, the meter should:
measure low resistance then return to high reading
Single phase motor speed is determined by the
number of stator poles
An electronically commutated motor (ECM) is designed to
provides proper air flow under various conditions
A capacitor analyzer is designed to read
the capacitance of a capacitor
Direction of rotation of a single phase induction motor is determined by;
the direction of current flow through the start winding
In electrical wiring a black colored wire usually indicates
the hot conductor
When resistors are wired in parallel
the voltage drop across each resistor will be the same as the applied source voltage
A three phase load requires a minimum of
three supply lines
A 240 volt, 4 wire circuit can be split into two; 120 circuits.
two 120 volts circuits between the hot legs and neutral
The electric meter on a house measures the ______ passing through it.
wattage
