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WorksheetsElectrical Prep Test
Total questions: 100
Worksheet time: 50mins
Current flow is:
Flow of voltage in a circuit
The impedance of a circuit
The inductive reactance of the circuit
The flow of electrons in the circuit
Impedance is
Opposition to alternate current flow
Electrical pressure
Amperage
Voltage applied to the circuit
Like charges
Attract one another
Repel each other
Are negative
Are positive
Any material that will readily release electrons is called
An insulator
A conductor
A resistance
A neutron
The symbol for current is
E
I
R
W
Which of the following materials would be best suited for use as a semi conductor?
Copper
Bakelite
Aluminum
Silicon
The safety ground conductor is usually color coded
Red or white
Black or white
Green or bare
White or bare
An electron has
No charge
A negative charge
A positive charge
Neutral charge
Resistance is
Opposition to current flow
Electrical pressure causing voltage flow
Enables amperage flow
opposition to alternate current only
How many watts of power are used by a heater operating at 240 volts and drawing 5 amps?
5 watts
48 watts
245 watts
1200 watts
Which of the following meters must use its internal power to check a load or circuit?
Ohmmeter
Voltmeter
Ammeter
Wattmeter
In electrical wiring, a black colored wire in an alternating current circuit usually indicates
The hot conductor
The neutral conductor
The ground conductor
The safety ground
Fuses are sized by
Amps & Watts
Volts & Watts
Watts & Ohms
Volts & Amps
What would be the result, if a 24 volt, 20-ohm low voltage contactor coil were wired in series in with 24 volt, 200-ohm control relay coil?
Neither the contactor nor control relay would operate.
Only the control relay would operate.
Only the contractor would operate.
Both the contractor and the control relay would operate.
Three defrost heaters, each 15 ohms are weird in parallel to a 120 volt power supply. How many watts of power will be used?
24 Watts
1800 Watts
2880 Watts
8 Watts
Which of the following is generally considered to be within the maximum allowable (plus or minus) supply voltage variation?
5%
15%
20%
30%
Capacitors are rated in
Amps & Volts
Microfarads & Watts
Volts &Ohms
Microfarads & Volts
When testing a capacitor with an analog or digital ohmmeter, the meter should;
Show no deflection or resistance and remain on an infinite reading .
Measure low resistance then return to a high reading.
Display a zero measurement and stay there.
Measure a precise resistance and stay there.
What is the term used to describe the output side of a transformer?
Low inductive side
High inductive side
Primary side
Secondary side
One horsepower is equal to _______ watts
3.415
746
1200
208
How much resistance must be placed in a 120 volt circuit in order to limit the current to 2 amps?
60 ohms
120 ohms
118 ohms
240 ohms
A parallel circuit contains a 18 ohm and 9 ohm resistor. The total resistance equals;
6 ohms
27 ohms
8 ohms
10 ohms
In a series circuit, the voltage drop across each resistance (load) will;
Depend on the wire gauge
Depend on the current to each resistor
Add up to the total resistance
Add up to equal the source voltage
The total resistance of a parallel circuit will be;
The sum of all resistance
Equal the largest resistance
Equal to the smallest resistance
Less than the smallest resistance
Which of the following statements about current is true?
Current is the same as Voltage
Current flow will increase when voltage increases
Current will increase when resistance increases
Current will decrease when voltage increases
When resistors are wired in parallel
The current any one resistor will be same the same as the total circuit current
The voltage drop across each resistor will be the same as the applied source voltage
The voltage drop across each resistor will depend on the value of each resistor
The total resistance is determined by adding the values
Which of the following is equal to 2.1kw?
21 watts
210 watts
2,100 watts
21,000 watts
Which of the following is equal to 100 milliamps?
1.0 amperes
10.0 amperes
0.10 amperes
0.01 amperes
A capacitor analyzer is designed to read;
The percentage of leakage
The capacitor voltage
The capacitive resistance of a capacitor
The capacitance of a capacitor
On an electric oil safety switch what changes the pressure signal to an electric signal?
Transducer
The circuit board
The bellows
Electronic processor
The electric meter on a house measures the ____ passing through it.
Voltage
Amperage
Wattage
Electronic processor
A three phase load requires a minimum of;
Three supply lines
Two supply lines and a ground
Three supply lines and a neutral
Two supply lines
Which of the following is the correct formula for determining wattage in an electrical circuit?
W=E times I
W=E / R
W=I / R
W=E times R
A parallel circuit consists of three resistorsR1= 30 ohms R2= 15 ohms R3= 10 ohms. If the current through R2= 4 amperes, what is the source voltage?
20 volts
60 volts
120 volts
220 volts
Three 300 ohm resistors are wired in parallel. The total resistance equals
100 ohms
300 ohms
600 ohms
900 ohms
An electronically commutated motor (ECM) is designed to;
Maintain a constant velocity
Have low starting torque
Operates at lower static pressure than axial fan motors
Provide proper airflow under various conditions
Resistance can be calculated by
E divided by I
W divided by E
E squared times W
I divided by E
Voltage can be calculated by
I divided by R
R divided by I
I times R
W divided by R
An ohmmeter should never be connected to
A resistor until it has been checked by other means
A coil or a winding of a compressor
A motor that has a grounded condition
A charged capacitor until it has been discharged
Which of the following would be considered an inductive load?
Electric heat strip
Start capacitor
Solid state relay
Electric motor
The voltage to ground of a "high leg" or "stinger leg" on a three phase open Delta system will be approximately;
240
220
208
120
A transformer has 1000 turns of wire in the primary coil and 500 turns in the secondary coil. If 120 volts are applied, the out put voltage will be;
120 KV
620 volts
60 volts
240 volts
A transformer has 1000 turns in the primary coil and 2000 turns in the secondary coil. If 120 volts are applied, the output voltage will be;
120 KV
620 volts
60 volts
240 volts
Which of the following is the symbol for impedance in an AC circuit?
W
Y
X
Z
When current flows in a two wire circuit (such as 120 volts) if a clamp on an amp meter is clamped around both wires. What measurement would you expect?
Zero amps due to cancellation of the two fields
Double the amps due to revering magnetic field
Damage the meter due to stronger magnetic field created
Should read the same as one wire being used
If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called
Capacitive reactance
Inductive reactance
Conductance
Influence
A diode is used to
Control the direction of electron flow
Increase inductive reactance
Convert DC current to AC current
Increase or Decrease frequency
A _______ is commonly used on a single phase capacitor start fractional horsepower compressor motor to disconnect the start winding after the motor starts
Lock out relay
NTC thermistor
Kinetic energy
Current relay
Direction of rotation of a single phase induction motor is determined by;
The direction of current flow through the start winding
The direction of current flow through the run winding
The number of poles in the motor
The voltage applied to the start winding
Single phase motor speed is determined by the
The number of coils in the stator
Number of stator poles
Supply Voltage
The circumference of the rotor
The capacitor start-capacitor run (cscr) motor provides
High running and low starting torque
Medium running and high starting torque
High starting and running torque
High running medium starting torque
To change the direction of a three phase motor
The motor must be replaced
Change the position of all three supply wires
Change the position of any two supply wires
The rotation of three phase motors cannot be changed
Capacitors are always connected _______ to the start winding
In parallel
In series
Through a relay
Through diode
Which meter is used to bench check a motor for shorts or open?
Ohmmeter
Voltmeter
Ammeter
Wattmeter
A solenoid valve operates on the principle of
Pressure differential
Temperature differential
Electromagnetism
Time and Temperature
When checking the windings of a three phase motor
All three terminals should show the different resistance
The pair with the highest resistance will indicate the other is common
All three terminals should show the same resistance
It is usually cheaper to replace a three phase motor than to test it
When testing the windings of a single phase motor
The pair of terminals with the highest resistance will indicate that the other terminal is the start
The common to start terminals show the lowest resistance
The common to run terminals show the lowest resistance
The start to run terminals show the lowest resistance
Direct Digital Control (DDC) is?
An electronic control that must manually adjusted
A digital control for controlling the electron flow in a series circuit
A digital control for controlling the electron flow in a parallel circuit
Electronic controls used for equipment operation and monitoring
A step up transformer increases
Power
Voltage
Resistance
Amperage
Transformers are rated according to
VA at the primary
VA at the secondary
Ohms at the primary
Ohms at the secondary
Utility companies usually supply residential home with _____ service
115V, single phase, three wire
240V, single phase, three wire
240V, three phase, three wire
480V, three phase, three wire
What connects to the terminals T1, T2, T3 on a contactor motor starter?
Power supply connection
Load connections
Coil connection and ground
Start / stop lead
Circuit breakers and fuses are primarily used to provide;
Protection of over impedance to the unit
Protection of impedance for the inductive loads
Protection from an overload of current
Switches used as protection devices
Excessive current can be caused by
Oversized wiring
Undersized fuse
Open circuit
Short circuit
A device with overload protection used to control a motor is a
Relay
Contactor
Selenium rectifier
Line starter
Relays are generally used to control inductive loads up to _____ amps
100
10
25
50
Contactors are rated according to the maximum amperage through the
Coil
Contacts
Thermostat
Fuse
What is the minimum number of wires required between two start/stop push button controls?
Depends on control design
1
2
3
If contacts become badly pitted, it is acceptable to
Sand the contacts
Replace the contacts or control
File the contacts
Replace the contacts or control with a solid state relay
The thermal overload contacts on a line starter are usually ______ reset
Manual
Automatic
Thermal
Time delay
The ________ drawing illustrates where the components are located in small appliances
Pictorial
Schematic
Ladder diagram
Outside
Which of the following motors is most energy efficient?
SIRC
ECM
PSC
Shaded Pole
On a good single compressor motor, which winding terminals have the highest resistance
Common to start
Run to start
Common to ground
Run to Ground
When testing a motor with an ohmmeter, the following measurements are recorded, common to run is 4 ohms, common to start is 6.2 ohms, run to start 10.2 ohms, and common to ground is 20.4 ohms. This is an indication of
Good safety ground
Grounded condition
Open in the Winding
Locked rotor condition
With a motor running at full load, voltmeter leads are placed on L1 and T1 terminals of the contactor. The voltmeter indicated no measurable voltage. This is an indication of
No voltage to the motor
Excessive resistance in the contacts
Good clean contacts
This is not a valid test
When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance will
Increase
Decrease
Remain the same
Increase proportionately to the Delta T
When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance will
Increase
Decrease
Remain the same
Increase proportionately to the Delta T
A transducer can create signal based on
Time
Turbulence
The specific gravity of the refrigerant
Pressure
A typical thermocouple used on a gas furnace can
Generate a small AC electrical current
Be used to power a shaded pole motor
Generate a small DC current
Generate up to 1 volt
To discharge a capacitor prior to ohmmeter testing;
Use a screwdriver across the capacitor terminals
Use a 15,000 or 20,000 ohm, 2 to 5 watt resistor
Touch the terminals with your bare finger
Use a 5,000 ohm, 2 to 5 watt resistor across the terminals
Which of the following is an acceptable temporary replacement for a run capacitor rated at 35MFD @440 VAC
50MFD @ 370VAC
47.5MFD @ 440VAC
Two 20MFD @ 440VAC in series -
37.5MFD @440VAC
The synchronous speed of a four pole, 60Hz single phase motor is;
3600 rpm
1500 rpm
3450 rpm
1800 rpm
The symbol for heating thermostat is represented by diagram
A
B
C
D
The symbol for pressure switch that closes on pressure rise represented by diagram
A
B
C
D
The symbol for pressure switch that opens on pressure rise represented by diagram
A
B
C
D
In the schematic, What voltage would be found across L1 to L2?
240 volts
480 volts
120 volts
0 volts
What voltage would be found across the condenser fan motor?
240 volts
480 volts
120 volts
0 volts
What voltage would be found across the transformer primary?
24 volts
240 volts
480 volts
0 volts
What voltage would be found across the fuse in line #10 with the thermostat closed?
0 volts
24 volts
120 volts
480 volts
What voltage would be found from terminal G to the load said of the transformer?
24 volts
0 volts
120 volts
240 volts
In the schematic, that voltage would be found across the contacts when energized in line #8?
0 volts
24 volts
240 volts
480 volts
In the schematic, that voltage would be found from terminal Y to the input side of the coil on line #11?
0 volts
24 volts
120 volts
240 volts
In the schematic, that voltage would be found from terminal Y to the output side of the coil on line #11?
0 volts
24 volts
120 volts
240 volts
When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contracts are closed. The compressor and condenser fan motors are short cycling. The blower motor is not running. This could be caused by;
A faulty coil on line #11
A blown fuse on #10
A faulty blower motor or blower relay
An open transformer
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;
CCH is energized
The contactor coil may be energized (line #11)
The HP, LP, overloads, or oil pressure switch are open (line #11)
BR is de-energized (line 8)
When troubleshooting the A/C system in the schematic, following conditions are found. The thermostat contacts are closed. The compressor and condenser fan switch at the thermostat is moved from the AUTO position to the FAN ON position, the blower runs. This could by;
A blown fuse on line # 10
A faulty blower relay coil
A faulty thermostat - AUTO / FAN ON switch
A faulty contractor
In the schematic, the crankcase heater will operate;
When the compressor is on
At all times
When compressor is off
When the oil pressure switch is on
In the schematic, coil on the line #11 does NOT control;
The compressor
The condenser fan motor
The crankcase heater
The blower motor
In schematic, coil on line #12 controls the
Thermostat
Blower motor relay
fan switch
transformer
In the schematic, if the fuse in L2 is blown the;
Blower motor will continue to operate
Compressor will continue to operate
Blower motor will single phase and burn out
Transform will be de-energized
