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WorksheetsBasic Electrical Final P.T
Total questions: 98
Worksheet time: 2hrs 16mins
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 alternating 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 alternating 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 with a 24 volt, 200-ohm control relay coil?
Neither the contactor nor control relay would operate.
Only the control relay would operate.
Only the contactor would operate.
Both the contactor and control relay would operate.
Three defrost heaters, each 15 ohms are wired 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 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 a 9 ohm resistor. The total resistance equals;
6 ohms.
8 ohms.
27 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 to the largest resistance.
equal to the smallest resistance.
less than the smallest resistance.
Which of the following statements about current is true?
Current flow is the same as voltage.
Current flow will increase when voltage increases.
Current flow will increase when resistance increases.
Current flow will decrease when voltage increases.
When resistors are wired in parallel;
the current through any one resistor will be 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 of each resistor.
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 electronic oil safety switch what changes the pressure signal to electrical signal?
Transducer.
The circuit board.
The bellows.
Electronic processor
The electric meter on a house measures the……………passing through it.
voltage
amperage
wattage
resistance
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 resistors. R1= 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.
operate at lower static pressure than axial fan motors.
provide proper air flow under various conditions.
Resistance can be calculated by;
E divided by I
W divided by E
E squared times W
I divided by
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 output voltage will be;
120 KV
620 volts
60 volts
240 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:
120 KV
620 volts
60 volts
240 volts
Which of the following is the symbol for Impedance in an AC circuit?
W.
X.
Y.
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.
Double the amps due to reversing 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.
increases inductive reactance.
convert DC current to AC current.
increase or decrease frequency.
A __________ is commonly used on a single phase capacitor start fractional horse power compressor motor to disconnect the start winding after the motor starts.
lock out relay
NTC thermistor
kinetic relay
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.
Capacitors are always connected …………….to the start winding.
in parallel
in series
through a relay
through a diode
Which meter is used to bench check a motor for shorts or open windings?
Ohmmeter
Voltmeter
Ammeter
Wattmeter
A solenoid valve coil operates on the principal of;
Press differential
Temperature differential
Electromagnetism
Time and temperature
When checking the windings of a three phase motor;
all three terminals should show different readings.
the pair with the highest resistance will indicate the other 1 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 be 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 use 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 homes 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 or motor starter?
Power supply connections
Load connections
coil connections and ground
start / stop leads
Circuit breakers & 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
Thermal
Automatic
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-phase 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 4 ohms, Common to start 6.2 ohms, Run to start 10.2 ohms, and Common to ground 20.4; This indicates a/an;
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 indicates 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 a 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 electrical 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 across the terminals
touch the terminals with your bare fingers
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@440VAC;
50MFD @ 370VAC
47.5MFD @440VAC
two 20MFD @ 440VAC in series
37.5MFD @ 440VAC
The synchronous speed of a four pole, 60 Hz single phase motor is;
3600 rpm
1500 rpm
3450 rpm
1800 rpm
The symbol for a heating thermostat is represented by diagram
A
B
C
D
The symbol for a pressure switch that closes on pressure rise represented by diagram
A
B
C
D
The symbol for a pressure switch that opens on pressure rise is represented by diagram
A
B
C
D
In the schematic, what voltage would be found across L1 to L2?
240 volts
1.20 volts
480 volts
0 volts
In the schematic, what voltage would be found-across the condenser fan motor?
240 volts
1.20 volts
480 volts
0 volts
In the schematic, what voltage would be found across the transformer primary?
24 volts
480 volts
240 volts
0 volts
In the schematic, what voltage would be found across the fuse in line #10 with the thermostat closed?
0 volts
1.20 volts
24 volts
240 volts
In the schematic, what voltage would be found from terminal G to the load side.of.the transformer?
24 volts
0 volts
120 volts
240 Volts
In the schematic, what voltage would be found across the contacts when energized in line #8?
0 volts
24 volts
240 volts
480 volts
In the schematic, what 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, what 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 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 coil on line #11.
a blown fuse on line #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, 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 blown fuse on line # 10.
a faulty blower relay coil.
a faulty thermostat - AUTO I FAN ON switch.
a faulty contactor.
In the schematic, the crankcase heater will operate;
when the compressor is on.
at all times.
when the compressor is off.
when the off pressure switch is on.
In the schematic, the coil on line #11 does NOT control;
the compressor
the condenser fan motor
the crankcase heater
the blower motor
In the schematic, the 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.
transformer will be de-energized.
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
