HVAC Electricity
Which of the following is equal to 100 milliamps?
0.10 amperes
Three 300 ohm resistors are wired in parallel. The total resistance equals;
100 ohms
How many watts of power are used by a heater operating at 240 volts and drawing 5 amps?
1200 watts
Which of the following is equal to 2.1KW?
2,100 Watts
The voltage to ground of a "high leg" or "Stinger leg" on a three phase open Delta system will be approximately;
208
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
A transformer has 1000 turns of wire in the primary roll 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
An ohmmeter should never by connected to;
A charged capacitor until it has been discharged
Any material that will readily release electrons is called:
A conductor
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
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 capacitor start fractional horse power compressor motor to disconnect the start winding after the motor starts.
Current relay
Resistance can be calculated by;
E divided by I
Which of the following would be considered an inductive load?
Electric motor
The safety ground conductor is usually color coded;
Green or bare
The symbol for current is:
I
Voltage can be calculated by;
I times R
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 testing a capacitor with an analog or digital thermometer, the meter should;
Measure low resistance then return to high reading
Capacitors are rated in;
Microfarads & Volts
Single phase motor speed is determined by the;
Number of stator poles
Which of the following meters must use its internal power to check a load or circuit?
Ohmmeter
What would be the result, if a 24 volt, 20-ohm low voltage contactor coil were wired in series with a 24 volt, 200-ohm control relay coil?
Only the control relay would operate
Impedance is:
Opposition to alternating current flow
Resistance is;
Opposition to current flow
An electronically commutated motor (ECM) is designed to;
Provide proper air flow under various conditions
Like charges:
Repel each other
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
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
Current flow is:
The flow of electrons in the circuit
In electrical wiring, a black colored wire in an alternating current circuit 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
On an electronic oil safety switch what changes the pressure signal to electrical signal?
Transducer
Fuses are sized by;
Volts & Amps
Which of the following is the correct formula for determining wattage in an electrical circuit?
W = E times I
The electric meter on a house measures the ________ passing through it.
Wattage
Which of the following is the symbol for impedance in an AC circuit?
Z
When current flows in a two wire circuit (such as 120 volts) if a clamp on amp meter is clamped around both wires, what measurement would you expect?
Zero amps due to cancelation of the two fields
