Electricity Flashcards
An accidental path of low resistance bypassing the intended path and allowing passage of an abnormally high amount of current is known as what?
Short circuit
How may the unit “hertz” be best described?
(a) revolutions per minute
(b) cycles per second
(c) coulombs per second
(d) revolutions per second
(b) cycles per second
In a series circuit what is the total applied voltage equal to?
(a) the total current divided by the total resistance
(b) the sum of the individual currents multiplied by the number of resistors
(c) the total resistance divided by the total current
(d) the sum of the individual voltage drops
(d) the sum of the individual voltage drops
[In a series circuit, Et = E1 + E2 + E3…]
In a series circuit, which value will remain unchanged at all places in the circuit?
(a) Inductance
(b) Voltage
(c) Current
(d) Resistance
(c) Current
[In a series circuit, It = I1 = I2 = I3…]
Four lamps are connected in series in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
(a) become brighter
(b) become dimmer
(c) burn with their original intensities
(d) all go out
(d) all go out
[In a series circuit, a burned out light bulb creates an open circuit, ie. no current flow though the circuit.]
Which of the following statements concerning a circuit with parallel connected resistors is correct?
(a) The voltage drop across each resistor is the same.
(b) The total current flow equals the reciprocal of the sum of the individual currents.
(c) The total voltage equals the sum of the individual voltages across each resistance.
(d) The total resistance equals the sum of the individual resistances.
(a) The voltage drop across each resistor is the same.
[In a parallel circuit, Et = E1 = E2 = E3…]
Which of the following statements is true concerning circuits with parallel connected resistances?
(a) The total current flow equals the sum of the individual currents.
(b) The total voltage equals the sum of the individual voltages across each resistance.
(c) The total current flow equals the reciprocal of the sum of the individual currents.
(d) The total resistance equals the sum of the individual resistance.
(a) The total current flow equals the sum of the individual currents.
[In a parallel circuit, It = I1 + 12 = I3…]
What statement is true concerning the total resistance of a parallel circuit?
(a) The total resistance is equal to the sum of the individual branch resistances divided by the number of branches.
(b) The total resistance is larger than that of the branch with the greatest resistance.
(c) The total resistance is smaller than that of the branch with the lowest resistance.
(d) The total resistance is equal to the sum of the individual branch resistances.
(c) The total resistance is smaller than that of the branch with the lowest resistance.
[In a parallel circuit, 1/Rt = 1/R1 + 1/R2 + 1/R3…]
Four lamps are connected in parallel in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
(a) become brighter
(b) all go out
(c) burn with their original intensities
(d) become dimmer
(c) burn with their original intensities
[In a parallel circuit, if one branch of the circuit goes out, current will still flow through the remaining branches with the same circuit voltage.]
Which statement is true concerning the total power consumed in a parallel circuit?
(a) The total power is always less than the power consumed by the smallest load.
(b) The total power is equal to the sum of the powers consumed by each individual load.
(c) The total power is never more than the power consumed by the largest load.
(d) The total power is the sum of the powers consumed by each load (resistor) divided by the
number of loads.
(b) The total power is equal to the sum of the powers consumed by each individual load.
Which of the electrical properties listed will always be the same across each component in a parallel circuit?
(a) Voltage
(b) Resistance
(c) Current
(d) Impedance
(a) Voltage
[In a parallel circuit, Et = E1 + E2 = E3…]
What will happen to the total circuit resistance when additional parallel circuits are added to a circuit?
(a) it will increase, causing a decrease in the line voltage
(b) it will decrease, causing an increase in the line voltage
(c) it will increase, causing a drop in the total load current
(d) it will decrease, causing an increase in the total load current
(d) it will decrease, causing an increase in the total load current
In a simple DC circuit, the resistance is held constant while the applied voltage is halved. What will be the effect on the current flow as compared to the original current?
(a) be divided by four
(b) remain the same
(c) be divided by two
(d) double
(c) be divided by two
Example:
If R=6 and E=3, then I=0.5
If R=6 and E=1.5, then I=0.25
A 125 volt DC motor is rated at 10 kW. What is the current rating of the motor?
(a) 4.6 amps
(b) 8.0 amps
(c) 46.2 amps
(d) 80 amps
(d) 80 amps
I = P / E I = 10kW / 125v I = 10000 / 125
If a circuit has resistances of 5, 10, and 20 ohms connected in parallel, what is the combined total resistance of the circuit?
(a) 1.5 ohms
(b) 2.9 ohms
(c) 17.5 ohms
(d) 35.0 ohms
(b) 2.9 ohms
1/Rt = 1/R1 + 1/R2 + 1/R3 1/Rt = 1/5 + 1/10 + 1/20 1/Rt = 0.35 Rt = 2.9
Which of the following statements is correct for the illustrated circuit in figure “B”? Illustration EL-0020
(a) ‘R1’, ‘R2’, and ‘R3’ are connected in series.
(b) The total resistance equals 1/R1 + 1/R2 + 1/R3.
(c) ‘R1’, ‘R2’, and ‘R3’ are connected in parallel.
(d) The voltages measured across ‘R1’, ‘R2’, and ‘R3’ are equal.
(a) ‘R1’, ‘R2’, and ‘R3’ are connected in series.
Referring to figure “B” of the illustration, what statement is true? (EL-0020)
(a) The current drawn by the circuit will be inversely proportional to the total resistance of the entire circuit.
(b) If the resistance values of the individual resistors are uniquely different, each resistor will have a uniquely different current draw.
(c) The current drawn by the circuit will be directly proportional to the total resistance of the entire circuit.
(d) The current drawn by an individual resistor will be proportional to the resistance of that resistor.
(a) The current drawn by the circuit will be inversely proportional to the total resistance of the entire circuit.
[If resistance increases, current will decrease. If resistance decreases, current will increase.]
Referring to figure “B” of the illustration, what statement is true? (EL-0020)
(a) The order of resistors connected in the series string has no impact on the total resistance. The total resistance of the circuit will be less than any one of the individual resistances.
(b) The order of resistors connected in the series string has an impact on the total resistance. If the largest resistance is last in the circuit, the total resistance will be more than if it is not.
(c) The order of resistors connected in the series string has no impact on the total resistance. The sum of the resistances is the total resistance of the circuit.
(d) The order of resistors connected in the series string has an impact on the total resistance. If the largest resistance is first in the circuit, the total resistance will be more than if it is not.
(c) The order of resistors connected in the series string has no impact on the total resistance. The sum of the resistances is the total resistance of the circuit.
[In a series circuit, Rt = the sum of all resistors, regardless of the resistor order.]
What statement is true concerning the electrical diagram shown in figure “B” of the illustration? EL-0019
(a) The voltages measured across ‘R1’, ‘R2’ and ‘R3’ will be different if ‘R1’, ‘R2’ and ‘R3’ have different values.
(b) The total resistance equals R1 + R2 + R3.
(c) ‘R1’, ‘R2’, and ‘R3’ are connected in parallel.
(d) ‘R1’, ‘R2’, and ‘R3’ are connected is series.
(c) ‘R1’, ‘R2’, and ‘R3’ are connected in parallel.
As shown in figure “A” of the illustration, with the switch closed what statement is true if ‘R1’ and ‘R2’ have unequal resistance values? EL-0019
(a) The energy dissipated in ‘R1’ will be the same as the energy dissipated in ‘R2’.
(b) The voltage drop across ‘R1’ will not be equal to the voltage drop across ‘R2’.
(c) The current flow through ‘R1’ will equal the current flow through ‘R2’.
(d) The current flow through ‘R1’ will differ from the current flow through ‘R2’.
(d) The current flow through ‘R1’ will differ from the current flow through ‘R2’.
[In a parallel circuit, current flow through each branch is inversely proportional to the resistance across each branch.]
What is the total resistance of figure “B” of the illustrated circuit if the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020
(a) 0.5 ohms
(b) 1.28 ohms
(c) 1.5 ohms
(d) 12 ohms
(d) 12 ohms
In a series circuit, Rt = R1 + R2 + R3
Rt = 3 + 4 + 5
Rt = 12 ohms
What is the total resistance of the electrical circuit illustrated in figure “B” if the resistance of R1 is 2 ohms, R2 is 4 ohms, and R3 is 4 ohms and the battery voltage is 6 volts? EL-0019
(a) 0.01 ohms
(b) 0.10 ohms
(c) 1.00 ohms
(d) 10.00 ohms
(c) 1.00 ohms
In a parallel circuit, 1/Rt = 1/R1 + 1/R2 + 1/R3
1/Rt = 1/2 + 1/4 + 1/4
1/Rt = 1 ohm
What will be the total current in figure “B” of the illustrated circuit with the switch closed if the applied voltage is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms, respectively? EL-0020
(a) 2 amps
(b) 6 amps
(c) 8 amps
(d) 10 amps
(a) 2 amps
I = E / R
In a series circuit, Rt = R1 + R2 + R3
Rt = 3 + 4 + 5 = 12 ohms
I = 24v / 12ohms
In figure “A” of the illustration, 12 volts is applied to the circuit where the resistance of R1 is 10 ohms and R2 is 10 ohms. what is the voltage across R2 when the switch is closed? EL-0020
(a) 1.2 volts
(b) 2 volts
(c) 6 volts
(d) 12 volts
(c) 6 volts
In a series circuit, Et = E1 + E2 and is proportional to their individual resistances.
Because R1 = R2, they split the voltage equally.
12v / 2 = 6v
What is the current flowing through R3 in figure “B” of the illustrated circuit when the switch is closed if the battery voltage is 12 VDC and resistance of R1 is 2 ohms, R2 is 3 ohms, and R3 is 6 ohms, respectively? EL-0019
(a) 2 amps
(b) 4 amps
(c) 6 amps
(d) 12 amps
(a) 2 amps
I3 = E3 / R3 I3 = 12v / 6 ohms
What would be the voltage drop across the parallel branches of the circuit shown in figure “B” of the illustration if the source voltage is 30 volts, the resistance for R1 is 10 ohms, the resistance for R2 is 10 ohms and the resistance for R3 is 10 ohms? EL-0032
(a) 5 volts
(b) 10 volts
(c) 20 volts
(d) 30 volts
(b) 10 volts
R1 + R2 = 5 ohms R3 = 10 ohms Rt = 15 ohms It = Et / Rt = 30v / 15 ohms / 2A I1 = 1 A E1 = I1 x R1 = 1A x 10 ohms = 10v
What would be the voltage drop across the series string of the circuit shown in figure “A” of the illustration if the source voltage is 30 volts, the resistance for R1 is 10 ohms, the resistance for R2 is 10 ohms and the resistance for R3 is 10 ohms? Illustration EL-0032
(a) 5 volts
(b) 10 volts
(c) 20 volts
(d) 30 volts
(d) 30 volts
In a parallel circuit, each branch has the same voltage as the total circuit voltage. Therefore:
Resistors 1+2 = 30v
Resistor 3 = 30v
What would be the total current draw of the circuit as shown in figure “A” of the illustration if the source voltage is 24 volts, the resistance for R1 is 12 ohms, the resistance for R2 is 24 ohms, and the resistance for R3 is 36 ohms? Illustration EL-0032
(a) 0.33 amperes
(b) 0.75 amperes
(c) 1.25 amperes
(d) 1.33 amperes
(d) 1.33 amperes
R1 + R2 = 36 ohms
Rt = 36x36 / 36+36 = 18 ohms
It = Et / Rt
It = 24v / 18 ohms
What would the total power consumed by the circuit as shown in figure “A” of the illustration if the source voltage is 12 volts, the resistance for R1 is 470 ohms, the resistance of R2 is 330 ohms, and the resistance of R3 is 800 ohms? Illustration EL-0032
(a) 90 milliwatts
(b) 180 milliwatts
(c) 360 milliwatts
(d) 720 milliwatts
(c) 360 milliwatts
P = I x E I = E / R P = E / R x E P = E^2 / R R1 + R2 = 800 ohms Rt = 800x800 / 800+800 = 400 ohms P = 12v^2 / 400 ohms = 0.36 watts
What would the total power consumed by the circuit as shown in figure “B” of the illustration if the source voltage is 12 volts, the resistance for R1 is 470 ohms, the resistance of R2 is 800 ohms, and the resistance of R3 is 330 ohms? Illustration EL-0032
(a) 57.5 milliwatts
(b) 115 milliwatts
(c) 230 milliwatts
(d) 460 milliwatts
(c) 230 milliwatts
P = I x E I = E / R P = E / R x E P = E^2 / R R1 and R2 = 470x800 / 470+800 = 296 ohms Rt = 296 + 330 = 626 ohms P = 12v^2 / 626 = 0.230 watts
How would a circuit with a blown fuse be described?
(a) an open circuit
(b) a bonded circuit
(c) a grounded circuit
(d) a short circuit
(a) an open circuit
Why is copper often used as an electrical conductor?
(a) has high resistance at low temperatures
(b) has a highly polished surface
(c) is able to pass current with little opposition
(d) holds insulation together well
(c) is able to pass current with little opposition
Which of the following characteristics is most critical in determining the wire gauge size of the cable to be used in a particular circuit?
(a) voltage rating
(b) current rating
(c) inductance per unit length
(d) weight per unit length
(b) current rating
What is the characteristic that is associated with an “instantaneous-trip” single- element type fuse?
(a) opens a circuit by using a time delay element with a magnetic trip
(b) allows a preset delay between over current and melting
(c) opens as soon as the load current exceeds its set point
(d) resets itself when the over current is corrected
(c) opens as soon as the load current exceeds its set point
For what purpose are time delayed or delayed action-type fuses used?
(a) permit momentary overloads without melting
(b) prevent opens in motor circuits
(c) guard lighting and electronic circuits
(d) prevent grounds in branch circuits
(a) permit momentary overloads without melting
Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced?
(a) Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.
(b) Use needle-nose pliers to remove fuse from the circuit.
(c) Short out the fuse before removing it from the circuit.
(d) Replace blown fuse with one of equal voltage and ampere capacity.
(d) Replace blown fuse with one of equal voltage and ampere capacity.
In a single element cartridge-type fuse, what type of protection is provided for lighting and general power applications?
(a) short-circuit protection using a fusible link
(b) sustained overload protection using a spring loaded soldered joint
(c) sustained overload protection using a fusible link
(d) short-circuit protection using a spring loaded soldered joint
(a) short-circuit protection using a fusible link
How are fuses rated?
(a) voltage and amperage only
(b) interrupting capacity only
(c) voltage, amperage, and interrupting capacity
(d) amperage only
(c) voltage, amperage, and interrupting capacity
In a dual element time-delay cartridge-type fuse, what type of protection is provided for motor applications?
(a) short-circuit protection using a spring loaded soldered joint AND sustained overload protection using a fusible link
(b) sustained overload protection using a spring loaded soldered joint only
(c) short-circuit protection using a fusible link AND sustained overload protection using a spring
loaded soldered joint
(d) short-circuit protection using a fusible link only
(c) short-circuit protection using a fusible link AND sustained overload protection using a spring
By what means does a molded-case circuit breaker provide protection against short circuits?
(a) use of an arc quencher
(b) use of a shading coil
(c) use of a bimetallic strip
(d) use of a magnetic trip unit
(d) use of a magnetic trip unit
How will a molded-case circuit breaker with a thermal trip unit react immediately after it has tripped, as a result of an overloaded motor circuit?
(a) The breaker handle will lock in the OFF position.
(b) The breaker cannot be reset to the ON position until the thermal element cools down.
(c) The breaker handle will lock in the TRIPPED position.
(d) The thermal element must be replaced after an overload trip has occurred before it can be
restored into service.
(b) The breaker cannot be reset to the ON position until the thermal element cools down.
How can a motor be protected from overheating due to sustained motor overload?
(a) thermal circuit breaker
(b) quick-acting fuse
(c) magnetic circuit breaker
(d) single element fuse
(a) thermal circuit breaker
How does a circuit breaker differ from a fuse?
(a) a circuit breaker melts and must be replaced, a fuse does neither
(b) a circuit breaker gives no visual indication of having opened the circuit, a fuse universally does
(c) a circuit breaker is enclosed in a tube of insulating material with metal ferrules at each end, a
fuse is not
(d) a circuit breaker trips to break the circuit and may be reset, a fuse may not be reset
(d) a circuit breaker trips to break the circuit and may be reset, a fuse may not be reset
Under voltage trips are frequently installed on switchboard circuit breakers for what reason?
(a) trip out generators in the event of severe arcing or sparking
(b) trip out the breaker if the generator over speeds by 5%, but continues to run
(c) trip out generators when there is reversal of power in the main circuit
(d) trip out the generator when there is insufficient voltage being delivered to distribution circuits
(d) trip out the generator when there is insufficient voltage being delivered to distribution circuits
Which of the following materials is a good electrical insulator?
(a) copper
(b) silver
(c) wood
(d) gold
(c) wood
When changing fuses, what safety precaution should be taken?
(a) wear safety glasses
(b) stand on a rubber mat
(c) wear rubber boots
(d) use a fuse puller
(d) use a fuse puller
When replacing fuses, what practice should be observed?
(a) to stand on a rubber mat and use rubber gloves
(b) to increase the fuse rating 10% to guard against ‘nuisance blowing’
(c) to use insulated pliers or screwdriver
(d) the fuse clips are straight, tight, and in good contact
(d) the fuse clips are straight, tight, and in good contact
When replacing a fuse with one of a ampere higher rating than the original, which of the following is true?
(a) It reduces the possibility of short circuits.
(b) It creates a larger voltage drop in the circuit being protected.
(c) It increases the efficiency of the equipment by allowing more current to be used.
(d) It endangers the apparatus it is supposed to protect.
(d) It endangers the apparatus it is supposed to protect.
In order to definitively determine whether or not fuse “2”, shown in the illustration is blown using an on-line testing technique, across what points would you connect the voltmeter leads? Illustration EL-0062
(a) the bottom of fuse “2” to the top of either fuse “1 or 3”
(b) the bottom of fuse “2” to the bottom of either fuse “1 or 3”
(c) the top of fuse “2” to the bottom of either fuse “1 or 3”
(d) the top of fuse “2” to the top of either fuse “1 or 3”
(a) the bottom of fuse “2” to the top of either fuse “1 or 3”
If a digital multimeter is set up as shown in figure “A” of the illustration, what would be displayed on the screen if the fuse being tested is not blown and has proper continuity? Illustration EL-0210
(a) 0.001 ohms
(b) OL volts
(c) 470 ohms
(d) OL ohms
(a) 0.001 ohms
To test fuses in an energized circuit, what testing apparatus or meter should be used?
(a) resistance meter
(b) voltmeter
(c) megohmmeter
(d) continuity tester
(b) voltmeter
What would cause a fuse to blow?
(a) the electrical current exceeds the rated value of the fuse
(b) the flow of current to the protection device is reversed
(c) an electric motor is stopped suddenly by opening a switch
(d) unequal resistors are connected in parallel
(a) the electrical current exceeds the rated value of the fuse
Due to the operating characteristics of the system, time lag fuses (or dual-element fuses) are necessary for use in what types of circuits?
(a) emergency lighting circuits
(b) main lighting circuits
(c) motor starting circuit
(d) general alarm circuits
(c) motor starting circuit
What is the basic similarity between a circuit breaker and a fuse?
(a) after a short or overload condition, both should open to de-energize the circuit
(b) after a short or overload condition, both must be reset to re-energize the circuit
(c) after a short or overload condition, both have to be replaced before the circuit can be re-
energized
(d) a circuit breaker and a fuse have no similarities
(a) after a short or overload condition, both should open to de-energize the circuit
When the operating handle of a molded-case circuit breaker is in the mid-position, what is the indication for the position of the circuit breaker?
(a) in the ‘tripped’ position
(b) in the ‘closed’ position
(c) in the ‘opened’ position
(d) in the ‘reset’ position
(a) in the ‘tripped’ position
What is meant by a ‘dead front’ switchboard?
(a) a switchboard with insulated switches and no exposed terminals
(b) a switchboard without safety hand rails nor rubber mats
(c) a switchboard without circuit breakers
(d) a switchboard without switches on it
(a) a switchboard with insulated switches and no exposed terminals
In figure “A” of the illustration, what is the position of the circuit breaker? Illustration EL-0033
(a) on
(b) off
(c) tripped
(d) not possible to determine
(b) off
Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out?
(a) Secure and tag the supply circuit breaker in the open position.
(b) De-energize the applicable switchboard bus.
(c) Bypass the interlocks.
(d) Station a man at the circuit supply switch.
(a) Secure and tag the supply circuit breaker in the open position.
What is the name of the type of motor control circuit that will not permit automatic restarting after power is restored, following a power failure?
(a) low voltage protection
(b) low voltage release
(c) overload lockout
(d) reduced voltage restart
(a) low voltage protection
Which of the listed items will stop a motor due to a reduction in voltage and automatically restart it when the voltage is restored to normal?
(a) Renewable link fuse
(b) Non-renewable link fuse
(c) Low voltage protection circuit
(d) Low voltage release circuit
(d) Low voltage release circuit
Capacitors can be used in electric distribution systems to improve power factor. This is accomplished by seesawing energy between the capacitor and what device or devices?
(a) capacitive loads
(b) inductive loads
(c) generator
(d) resistive loads
(b) inductive loads
When working on electrical circuits containing large capacitors, in addition to de- energizing the circuit, which of the listed precautions should also be taken?
(a) Measure capacitor insulation resistance.
(b) Keep all radio equipment away.
(c) Check capacitor circuit polarity.
(d) Discharge the capacitor through a 50,000 ohm resistor.
(d) Discharge the capacitor through a 50,000 ohm resistor.
Capacitors are commonly used on DC power supply circuits for engine room automation consoles. For what functional purpose are they primarily used in this application?
(a) filter out ‘ripple’ from rectification
(b) decrease the average value of the output voltage
(c) prevent overloads
(d) act as a permanent load
(a) filter out ‘ripple’ from rectification
[Like an accumulator.]
A capacitor is to be tested with a digital multimeter set up to measure ohms. If the meter is connected to a shorted capacitor, how would the meter display respond?
(a) immediately display a value of OL with the value then continuously dropping to a low value
(b) immediately display a value of OL which remains at OL
(c) immediately display a very low resistance value which remains low
(d) immediately display a very low resistance with the value then continuously rising to a value of
OL
(c) immediately display a very low resistance value which remains low
After prior isolation and lockout/tagout procedures are performed, which electrical device requires discharging any stored electrical energy before any work may safely begin?
(a) resistor bank
(b) capacitor
(c) potential transformer
(d) choke coil
(b) capacitor
What effect will increasing the power source frequency have in a capacitive circuit?
(a) it will not have any effect on the average current value (b) it will decrease the average current in the circuit
(c) it will increase the average current in the circuit
(d) it will not have any effect on the capacitive reactance
(c) it will increase the average current in the circuit
What will happen to an electrical coil when the direct current flowing through the coil is increasing?
(a) the increasing current produces a voltage in opposition to the applied voltage
(b) the increasing current reduces the power consumed
(c) the increasing current reduces the amount of flux produced
(d) the increasing current changes the coil’s impedance
(a) the increasing current produces a voltage in opposition to the applied voltage
In which of the situations listed will a megohmmeter give the most accurate readings?
(a) While the machine is in operation.
(b) Immediately prior to restarting the machine.
(c) While the machine is discharging static electricity.
(d) When the machine has been shut down and grounded for a period of 15 minutes.
(d) When the machine has been shut down and grounded for a period of 15 minutes.
When troubleshooting a lead-acid storage battery, what is the best method for detecting a weak or dead cell?
(a) comparing the specific gravity of the electrolyte in each cell
(b) taking an open circuit voltage test of individual cells
(c) taking each cell’s temperature with a calibrated mercury thermometer
(d) visually inspecting the electrolyte levels of each cell
(a) comparing the specific gravity of the electrolyte in each cell
What could prevent a lead-acid battery from accepting a full charge?
(a) Attempting to force charging current into the battery in the opposite direction to that which occurs during discharge.
(b) Topping off low electrolyte levels (due to evaporation) with distilled water.
(c) Leaving the battery in a discharged condition for a great length of time.
(d) Coating terminal posts with an anti-oxidant grease approved for battery use.
(c) Leaving the battery in a discharged condition for a great length of time.
Grounds occurring in electrical machinery as a result of insulation failure may result from deterioration over time and excessive heat. What could be another contributing cause?
(a) extended periods of vibration
(b) extended operation at normal loads
(c) extended periods of operation at low ambient temperature
(d) extended periods of operation at low load
(a) extended periods of vibration
The individual 12 volt lead-acid batteries, when connected as shown in the illustration, as a battery bank would produce how many volts? EL-0070
(a) 12 volts
(b) 24 volts
(c) 36 volts
(d) 48 volts
(a) 12 volts
[When connected in parallel, the voltage is consistent across the circuit.]
What is the ampere-hour rating of a lead-acid battery that can deliver 20 amperes continuously for 10 hours?
(a) 20
(b) 40
(c) 200
(d) 400
(c) 200
[20 amps x 10 hours]
Three 12 volt, lead-acid, batteries connected in series will develop how many volts?
(a) 12 volts
(b) 24 volts
(c) 36 volts
(d) 48 volts
(c) 36 volts
[When connected in series, the total voltage is the sum of the individual voltages, ex: 12+12+12=36]
Why should battery rooms we well ventilated during the charging of storage batteries?
(a) without ventilation the battery will not take a full charge
(b) without ventilation excessive gassing will occur
(c) highly explosive gases will otherwise accumulate
(d) highly poisonous gases are released
(c) highly explosive gases will otherwise accumulate
Which of the following statements describes the effects of ambient temperature on local action within lead-acid storage batteries?
(a) At 90°F all local action virtually ceases.
(b) Increasing ambient temperature decreases local action.
(c) Ambient temperature has no effect on local action.
(d) Increasing ambient temperature increases local action.
(d) Increasing ambient temperature increases local action.
Why are nickel-cadmium batteries superior to lead-acid batteries for standby service?
(a) they are able to hold their charge for long periods of time without recharging
(b) they need fewer cells connected in series for the same voltage and require less mounting
space
(c) the have higher output voltages for the same number of cells and require no maintenance
(d) they have a lower cost of acquisition
(a) they are able to hold their charge for long periods of time without recharging
When a low input voltage is delivered to a transformer which then produces a high output voltage, what is the proper name for the transformer type?
(a) step-up transformer
(b) primary transformer
(c) step-down transformer
(d) secondary transformer
(a) step-up transformer
Relative to the number of turns of a secondary winding of a step-up transformer, what will be the number of turns of a primary winding?
(a) the primary winding will have fewer turns than the secondary winding
(b) the primary winding will have the same number of turns but smaller wires than the secondary
winding
(c) the primary winding will have twice as many turns as the secondary winding
(d) the primary winding will have more turns than the secondary winding
(a) the primary winding will have fewer turns than the secondary winding
Which of the following statements is true concerning step-down transformer operation?
(a) The voltage supplied to the primary side is lower than the voltage produced by the secondary side.
(b) The voltage supplied to the primary side is greater than the voltage produced by the secondary side.
(c) The kVA consumed by the primary side is greater than the kVA produced by the secondary side.
(d) The current drawn by the primary side is greater than the current delivered from the secondary side.
(b) The voltage supplied to the primary side is greater than the voltage produced by the secondary side.
Which of the following statements describes the difference between the primary windings and the secondary windings of a 2:1 step-down voltage transformer?
(a) The secondary windings can only provide half as much current as the primary windings.
(b) The secondary windings have twice as much resistance as the primary windings.
(c) The secondary windings use smaller wires than the primary windings.
(d) The secondary windings have half as many turns as the primary windings.
(d) The secondary windings have half as many turns as the primary windings.
Propulsion AC generators creating 4160 VAC use transformers to provide nominally 120 VAC to the automatic voltage regulator. What is the turns ratio of this step-down transformer?
(a) 1:4
(b) 40:1
(c) 35:1
(d) 4:1
(c) 35:1
[4160 / 120 = 35]
What are the operating characteristics of a step-down potential transformer in terms of the secondary load?
(a) reduced voltage and reduced current
(b) reduced voltage and increased current
(c) reduced power (kVA)
(d) reduced current and increased voltage
(b) reduced voltage and increased current
What is the primary means by which an electrical maintenance worker is protected from electrical hazards while performing work on an electrical circuit?
(a) using the appropriate personal protective equipment
(b) shutting down the necessary equipment
(c) performing a lockout/tagout procedure
(d) posting of safety warning signs
(c) performing a lockout/tagout procedure
In general, why are nickel-cadmium storage batteries superior to lead-acid batteries?
(a) they can remain idle and keep a full charge for a long time
(b) they need fewer cells in series and use less mounting space
(c) they are less costly to replace
(d) they put out higher voltages and require no maintenance
(a) they can remain idle and keep a full charge for a long time
What is a hydrometer used to measure?
(a) specific gravity of a battery electrolyte
(b) amount of potable water a vessel is taking on
(c) power developed by a salt water service pump
(d) water pressure in a deck pipeline
(a) specific gravity of a battery electrolyte
Which of the following statements concerning nickel-cadmium batteries is true?
(a) Nickel-cadmium batteries should only be discharged 50% before recharging.
(b) When mixing electrolyte always add acid to the water.
(c) The state of charge cannot be determined by the specific gravity values.
(d) The electrolyte of an idle nickel-cadmium battery must be replaced monthly to maintain battery
condition.
(c) The state of charge cannot be determined by the specific gravity values.
In terms of the battery electrolyte, when performing maintenance of alkaline batteries what should be done?
(a) checking the electrolyte weekly using a hydrometer
(b) replacing the electrolyte every 5 years
(c) wearing protective gloves and goggles when handling electrolyte
(d) replacement of the electrolyte when the volts per cell drops below 1.8 VDC
(c) wearing protective gloves and goggles when handling electrolyte
Why are transformer cores laminated?
(a) to reduce secondary flux
(b) to reduce eddy currents
(c) to reduce flux leakage flux
(d) to reduce hysteresis
(b) to reduce eddy currents
The nominal open-circuit voltage of one cell of a fully charged lead-acid battery is approximately how many volts?
(a) 2 volts
(b) 1.5 volts
(c) 12 volts
(d) 6 volts
(a) 2 volts
How many cells are within in a 24 volt lead-acid battery?
(a) twelve cells
(b) three cells
(c) six cells
(d) four cells
(a) twelve cells
[A lead acid battery contains 2v per cell.]
In the illustrated views of a lead acid battery as shown in figures “A” and “B”, what battery component has the sole function of preventing the individual plates in the negative plate group from coming into direct contact with the individual plates in the positive plate group? Illustration EL-0031
(a) separators
(b) cell dividers
(c) casing
(d) series connecting straps
(a) separators
As shown in the cutaway view of the lead acid battery in figure “A” of the illustration, if one half of the battery’s cells are revealed by the cutaway section (with the other half remaining hidden from view), what is the nominal output voltage of the battery? EL-0031
(a) 6 volts
(b) 7.5 volts
(c) 12 volts
(d) 18 volts
(c) 12 volts
[A 12v lead acid battery has six cells of 2v each.]
A load is connected across the secondary of the step up transformer shown in figure “B” of the illustration and the current drawn by the load is 10 amps. If the turns ratio is 1 to 10 and the input voltage is 110 VAC, what will be the current drawn by the primary? Illustration EL-0055
(a) 1000 amps
(b) 100 amps
(c) 1 amp
(d) 10 amps
(b) 100 amps
Primary voltage = 110 VAC (given)
Primary current = 100 amps (because Ep x Ip = Es x Is)
Secondary voltage = 1100 VAC (because 110x10)
Secondary current = 10 amps (given)
If the illustrated device in figure “B” has a step-up ratio of 10 to 1 what voltage would be measured at the secondary shortly after the primary of the device is connected to 110 volts DC with a current of 12 amps? Illustration EL-0055
(a) 1000 volts
(b) 1100 volts
(c) 110 volts
(d) 0 volts
(d) 0 volts
[A voltage transformer is for AC, not DC.]
A load with an impedance of 440 ohms is connected across the secondary of the step up transformer shown in figure “B” of the illustration. If the input voltage is 110 VAC and the turns ratio is 1 to 10, what will be the primary current? EL-0055
25 amps
110v x 10 = 1100v on the secondary winding
1100v / 440ohms = 2.5 amps on the secondary
2.5 x 10 = 25 amps on the primary
The wet-cell storage batteries shown in the illustration are connected in what configuration? Illustration EL-0070
(a) series
(b) compound
(c) tandem
(d) parallel
(d) parallel
[The negative terminals are all tied together, as are the positive terminals all tied together.]
What would be the terminal voltage and ampere-hour capacity of the battery bank if each battery was rated at 50 amp-hours and 6 volts? Illustration EL-0107
(a) 12 volts and 100 ampere-hours
(b) 12 volts and 200 ampere-hours
(c) 6 volts and 50 ampere-hours
(d) 24 volts and 50 ampere-hours
(a) 12 volts and 100 ampere-hours
[The batteries are connected in series-parallel.]
What would be the terminal voltage and ampere-hour capacity of the battery bank
illustrated if each battery was rated at 75 ampere-hours and 12 volts? EL-0107
(a) 12 volts and 150 ampere-hours
(b) 24 volts and 150 ampere-hours
(c) 48 volts and 300 ampere-hours
(d) 24 volts and 75 ampere-hours
(b) 24 volts and 150 ampere-hours
In the illustration, 1, 2, 3 and 4 are 12 volt batteries. What will be the nominal voltage as read by a voltmeter across the output of the battery bank? Illustration EL-0107
(a) 12 volts
(b) 48 volts
(c) 24 volts
(d) 6 volts
(c) 24 volts
As shown in the illustration, the wet-cell storage batteries are connected in what configuration? EL-0071
(a) series
(b) parallel
(c) tandem
(d) compound
(a) series
If the voltage supplied to the lighting circuit is 110 volts, how much current is drawn by a 100 watt light bulb?
(a) 0.91 amps
(b) 0.08 amps
(c) 1.10 amps
(d) 90.9 amps
(a) 0.91 amps
Two 100 watt light bulbs rated at 100 volts are connected in parallel across a 100 volt power supply. What will be the total power consumed by the two bulbs?
(a) 200 watts
(b) 50 watts
(c) equal to the product of the amperes times the voltage in each branch
(d) 100 watts
(a) 200 watts
Which of the electronic schematic symbols represents the capacitor illustrated in figure 2 of the illustration? Illustration EL-0015
(a) D
(b) C
(c) A
(d) B
(b) C
How many watts of power is equal to one horsepower?
(a) 500 watts
(b) 746 watts
(c) 663 watts
(d) 1,000 watts
(b) 746 watts
Which of the illustrated resistors represents the schematic symbol shown in figure “C”? Illustration EL-0021
(a) figure “6”
(b) figure “10”
(c) figure “4”
(d) figure “7”
(a) figure “6”
[Note the four taps.]
As shown in figure “6” of the illustration, what does the symbol represent as used in electrical drawings? Illustration EL-0026
(a) maintaining type push button with an electrical interlock
(b) normally closed contact held open mechanically by an interlock
(c) limit switch with one set of normally open contacts
(d) maintaining type push button with a mechanical interlock
(d) maintaining type push button with a mechanical interlock
Which of the illustrated schematic symbols represents the type of switch pictured in figure “F” of the illustration? Illustration EL-0026
(a) 6
(b) 3
(c) 2
(d) 1
(b) 3
In figure “1” of the illustration, what type of circuit breaker trip element is featured? EL- 0033
(a) ambient compensated trip
(b) shunt trip
(c) magnetic trip
(d) thermal trip
(d) thermal trip
In figure “1” of the illustration, what are the trip characteristics associated with this type of circuit breaker? Illustration EL-0033
(a) inverse-time delay characteristic for short-circuit protection
(b) instantaneous trip characteristic for short-circuit protection
(c) instantaneous trip characteristic for sustained overloads
(d) inverse-time delay characteristic for sustained overloads
(d) inverse-time delay characteristic for sustained overloads
[Such as heat overload.]
What is the resistance reading at “2” on the megger scale shown in figure “A” of the illustration? Illustration EL-0044
(a) 40 megohms
(b) 40,000 ohms
(c) 400 ohms
(d) 40 ohms
(a) 40 megohms
As shown in figures “B” and “C” of the illustration, what should be the switch position and which test lead terminal jacks should be used if your intent is to measure DC currents anticipated as high as 200 milliamps? Illustration EL-0047
(a) switch position “6” and terminal jacks “1 and 4”
(b) switch position “6” and terminal jacks “2 and 4”
(c) switch position “7” and terminal jacks “1 and 4”
(d) switch position “7” and terminal jacks “2 and 4”
(a) switch position “6” and terminal jacks “1 and 4”
Which electrical schematic symbol represents a normally open thermostat? Illustration EL-0059
(a) 8
(b) 2
(c) 7
(d) 9
(d) 9
What is the name of the semiconductor that decreases in resistance with an increase in temperature?
(a) resistor
(b) thermistor
(c) thermopile
(d) diode
(b) thermistor
What is the name of the device shown in figure “2” of the illustration? Illustration EL-0068
(a) rectifier bridge
(b) power rectifier diode
(c) light-emitting diode
(d) silicon-controlled rectifier
(b) power rectifier diode
Which of the pictured solid-state semiconductor devices in the illustration is a rectifier bridge? Illustration EL-0068
(a) 2
(b) 5
(c) 3
(d) 4
(c) 3
Which of the pictured solid state semiconductor devices is a light-emitting diode? EL- 0068
(a) 1
(b) 2
(c) 4
(d) 7
(d) 7
The turns ratio of the tapped step down transformer shown in figure “C” of the illustration is four to one and all taps are evenly spaced. If 120 volts were applied to terminals ‘H1’ and ‘H3’, what would appear at ‘X1’ and ‘X2’? EL-0082
(a) 15 volts
(b) 30 volts
(c) 480 volts
(d) 960 volts
(a) 15 volts
Primary = 180 volts total, 60 across each tap.
Secondary = 45 volts total (180/4)
X1 and X2 = 15 volts (45/3)
The turns ratio of the tapped step down transformer shown in figure “C” of the illustration is four to one and all taps are equally spaced. If 440 volts were applied between ‘H1’ and ‘H4’, what would appear across ‘X1’ and ‘X4’? EL-0082
(a) 110 volts
(b) 220 volts
(c) 440 volts
(d) 1760 volts
(a) 110 volts
[440 / 4 = 110]
As shown in figure “B” of the illustration, if the source voltage at the branch circuit
breaker is 220 VAC, what would be the applied voltage to the load? EL-0083
(a) 55 volts
(b) 110 volts
(c) 165 volts
(d) 220 volts
(a) 55 volts
[25% of 220 VAC = 55]
As shown in figure “A” of the illustrated three phase alternator showing the stator winding connections, what can be said about the output line current? EL-0074
A line current is the phase current divided by 1.73
B line current is 1.73 times the phase current
C there is no relationship between line current and phase current
D line current is equal to phase current
D line current is equal to phase current
[In WYE connections, line current is equal to phase current.]
As shown in figure “A” of the illustrated three phase alternator showing the stator winding connections, what can be said about the output line voltage? EL-0074
A line voltage is 1.73 times the phase voltage
B line voltage is equal to the phase voltage
C line voltage is phase voltage divided by 1.73
D there is no relationship between line voltage and phase voltage
A line voltage is 1.73 times the phase voltage
[In WYE connections, line voltage is 1.73 times the phase voltage.]
Which of the listed figures shown in the illustration represents a three phase transformer connected in a wye-delta configuration? Illustration EL-0084
(a) 1
(b) 2
(c) 3
(d) 4
(d) 4
[Note that the WYE connections in the illustration are connected on a common neutral bus, ‘N’]
In figure “2” of the diagram shown in the illustration, the three phase power transformer has a step-down turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals ‘A1-B1-C’1, what voltage should develop across terminals ‘A2-B2-C2’? Illustration EL- 0084
(a) 762 volts
(b) 64 volts
(c) 190 volts
(d) 110 volts
(d) 110 volts
[Wye to wye]
In figure “2” of the diagram shown in the illustration, the three phase power transformer has a step-down turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals ‘A1-B1-C’1, what voltage should develop across terminals ‘A2-B2-C2’? Illustration EL- 0084
(a) 762 volts
(b) 64 volts
(c) 190 volts
(d) 110 volts
(d) 110 volts
[Wye to wye]
A carbon resistor has a resistance of 50 ohms, and a tolerance of 5 percent. What would be the respective colors indicated for bands 1, 2, 3 and 4 for this resistor as shown in figure “A” of the illustration? EL-0103
(a) green, black, black, and silver.
(b) green, black, black, and gold.
(c) gray, black, brown, and silver.
(d) gray, black, brown, and gold.
(b) green, black, black, and gold.
Green = 5 Black = 0 Black = multiplier of 1 Gold = tolerance of 5%
What would be the resistance tolerance of a carbon resistor which is color coded as red, violet, brown, and silver in bands 1 thru 4 respectfully as shown in figure "A" of the illustration? A 1% B 5% C 10% D 20%
C 10%
[Silver band = tolerance of 10%]
A carbon resistor has the following color bands; band 1 is yellow, band 2 is violet, band 3 is orange, and band 4 is silver. What is the ohmic value of the resistor, as well as the tolerance? A 47 ohms + or - 10% B 7400 ohms + or - 5% C 47,000 ohms + or - 10% D 740,000 ohms + or - 5%
C 47,000 ohms + or - 10%
Yellow = 4 Violet = 7 Orange = multiplier of 1000 Silver = tolerance of 10%
What would be the ohmic value of a carbon resistor if the color bands 1, 2, 3, and 4 were yellow, green, orange, and gold respectively. A 42.75 to 47.25 ohms B 4,275 to 4,725 ohms C 42,750 to 47,250 ohms D 427,500 to 472,500 ohms
C 42,750 to 47,250 ohms
Yellow = 4 Green = 5 Orange = multiplier of 1000 Gold = +/- 5% 45000 - 5% = 42750 45000 + 5% = 47250
What would be the ohmic value of a carbon resistor if the color bands 1, 2, 3, and 4 were yellow, green, orange, and gold respectively. A 42.75 to 47.25 ohms B 4,275 to 4,725 ohms C 42,750 to 47,250 ohms D 427,500 to 472,500 ohms
C 42,750 to 47,250 ohms
Yellow = 4 Green = 5 Orange = multiplier of 1000 Gold = +/- 5% 45000 - 5% = 42750 45000 + 5% = 47250
Which of the following statements is true concerning the following illustration? Illustration EL-0028
(a) The figures represent a basic AC generator
(b) Maximum voltage is produced in figures A and C
(c) The figures represent a basic DC generator
(d) Field polarity reverses from figures A to B and C to D
(c) The figures represent a basic DC generator
By what means is DC generator output voltage decreased?
(a) decreasing armature resistance
(b) increasing field resistance
(c) increasing armature resistance
(d) decreasing field resistance
(b) increasing field resistance
What is the purpose of the commutator and brushes on a DC generator?
(a) provide a sliding contact method to excite the field
(b) transfer generated direct current voltage from the armature to the line
(c) convert the alternating current voltage generated within the armature to a direct current voltage
(d) reduce sparking between the armature and the carbon brushes
(c) convert the alternating current voltage generated within the armature to a direct current voltage
What two factors determine the magnitude of the generated voltage of a DC generator?
(a) The rotational speed of the armature and the magnetic strength of the field flux.
(b) The armature current draw and the magnetic strength of the field flux.
(c) The rotational speed of the field and the magnetic strength of the armature flux.
(d) The rotational speed of the armature and the armature current draw.
(a) The rotational speed of the armature and the magnetic strength of the field flux.
By what means is a DC generator prevented from becoming motorized if paralleling is accomplished without an equalizer?
(a) reverse current relay
(b) over speed trip
(c) back pressure trip
(d) governor controls
(a) reverse current relay
A DC generator which is used to supply direct current in order to provide magnetizing current to an AC generator field is commonly known as what?
(a) exciter
(b) rotor
(c) stator
(d) armature
(a) exciter
Why are space heaters provided on larger generators?
(a) maintain rotor and stator winding temperatures above the dew point to prevent the formation of condensation
(b) prevent condensation in the lube oil
(c) prevent electrolysis due to condensation in the bearings
(d) keep the machine at ambient temperature of the machinery space
(a) maintain rotor and stator winding temperatures above the dew point to prevent the formation of condensation
In a shunt-wound DC generator, with what generator component are the shunt field windings connected in parallel with?
(a) the compensating windings
(b) the armature circuit
(c) the series field winding
(d) the interpoles
(b) the armature circuit
[In a shunt wound motor, the shunt field is in parallel with the armature.]
In a series wound motor, the current passing through the field windings also passes through what component?
(a) reactance comparator
(b) shunt field
(c) laminations
(d) armature
(d) armature
[In a series wound motor, all components are in series.]
As load is added to a DC shunt motor, how will the motor respond?
(a) stop
(b) speed up
(c) maintain the same speed
(d) slow down slightly
(d) slow down slightly
[On DC shunt motors, as load increases, voltage decreases.]
Which of the following types of DC motors is considered to produce the highest starting torque?
(a) cumulative-compound wound
(b) series wound
(c) shunt wound
(d) differential-compound wound
(b) series wound
How is the speed of a series wound winch motor controlled?
(a) over current protection devices in the motor
(b) the weight of the load on the cargo boom
(c) varying the voltage applied to the motor
(d) a hydraulic speed-limiting governor
(c) varying the voltage applied to the motor
What type of DC motor is never connected to a belt driven load?
(a) compound wound
(b) shunt wound
(c) permanent magnet
(d) series wound
(d) series wound
What type of DC motor has extremely high starting torque, but has poor inherent speed regulation?
(a) compound wound
(b) permanent magnet
(c) shunt wound
(d) series wound
(d) series wound
The wiring diagram found in figure “C” of the illustration represents what type of DC motor? (EL-0054)
(a) shunt wound
(b) compound wound with long shunt
(c) series wound
(d) compound wound with short shunt
(c) series wound
EL-0054
Figure A: shunt (parallel) wound
Figure B: compound (series and shunt) wound
Figure C: series wound
How can the direction of rotation of a DC motor be reversed?
(a) wiring the field and armature in series
(b) reversing the field or armature connections
(c) reversing both the field and the armature connections (d) wiring the field and armature in parallel
(b) reversing the field or armature connections
What is the correct name for a variable resistor wired in series with the shunt field for the purposes of manually controlling generator output voltage?
(a) bridge
(b) rheostat
(c) variable shunt strip
(d) bleeder resistor
(b) rheostat
What statement is true concerning speed control of a shunt wound DC motor?
(a) For armature rheostat control, the greater the resistance the lower the motor speed. For field rheostat control, the greater the resistance the lower the motor speed.
(b) For armature rheostat control, the greater the resistance the higher the motor speed. For field rheostat control, the greater the resistance the higher the motor speed.
(c) For armature rheostat control, the greater the resistance the lower the motor speed. For field rheostat control, the greater the resistance the higher the motor speed.
(d) For armature rheostat control, the greater the resistance the higher the motor speed. For field rheostat control, the greater the resistance the lower the motor speed.
(c) For armature rheostat control, the greater the resistance the lower the motor speed. For field rheostat control, the greater the resistance the higher the motor speed.
With what device is the simplest method of controlling the terminal voltage of compound-wound DC generator?
(a) carbon pile regulator in series with the load
(b) hand-operated field rheostat connected in series with the shunt field circuit
(c) balance coil diverting neutral current through the shunt field
(d) separate exciter in a series with the shunt field
(b) hand-operated field rheostat connected in series with the shunt field circuit
The counter EMF of a DC motor is maximum when the __________.
(a) armature is not turning
(b) motor is almost up to rated speed
(c) armature has just begun to turn
(d) motor is at rated speed
(d) motor is at rated speed
Which of the following components are used to convert alternating current produced in the DC generator armature windings to direct current?
(a) Armature and equalizer
(b) Rotor and interpoles
(c) Field and exciter
(d) Commutator and brushes
(d) Commutator and brushes
Why are modern DC generators fitted with commutating poles?
(a) they reduce the load on the main poles
(b) they reduce spring pressure on the brushes
(c) they prevent motorizing
(d) they reduce sparking
(d) they reduce sparking
What can cause uneven wear of the commutator surface on a direct current generator?
(a) excessive operation at light load
(b) incorrect brush staggering
(c) rapid change in load
(d) unequal pole spacing
(b) incorrect brush staggering
What would excessive sparking at the brushes of a running DC motor be an indication of?
(a) water vapor absorption
(b) increased brush capacity
(c) normal operation
(d) a dirty commutator
(d) a dirty commutator
How may chattering of the collector/slip ring brushes on a generator be remedied?
(a) lubricating brush holders
(b) reinsulating the brushes
(c) cleaning the collector rings with a canvas wiper
(d) increasing length of pigtail
(c) cleaning the collector rings with a canvas wiper
What may cause brush sparking in a DC generator during commutation?
(a) eddy currents in the armature core
(b) excessive brush pressure
(c) misalignment of the brush rigging
(d) hysteresis in the armature core
(c) misalignment of the brush rigging
Universal motors will operate on AC or DC current. In what application is this type of motor generally?
(a) forced draft fans
(b) large pump motors
(c) portable tools
(d) turbo electric main motors
(c) portable tools
What is the item referred to as a pigtail on a DC motor brush rigging?
(a) brush holder
(b) uninsulated wire
(c) flexible spring adjuster
(d) feather spring
(b) uninsulated wire
What is the function of the interpoles installed in DC motors?
(a) To provide greater torque by strengthening the main field.
(b) To limit the production of counter-electromotive force.
(c) To provide sparkless commutation without having to shift the brushes.
(d) To limit the starting surge current.
(c) To provide sparkless commutation without having to shift the brushes.
[Interpoles keep the magnetic field in more or less the same place.]
How can the nominal resistance value of a typical carbon resistor in a circuit best be determined?
(a) by the band markings on the resistor
(b) by the resistance value written on the resistor
(c) by the physical size of the resistor
(d) by the single solid body color of the resistor
(a) by the band markings on the resistor
Alternating current circuits may develop resistance, inductance and capacitance. What would be the unit of measure used in measuring the inductance of a wound coil? A ohms B mhos C henrys D farads
C henrys
Alternating current circuits may develop resistance, inductance, and capacitance. What is the unit of measure for expressing capacitance? A ohms B mhos C henrys D farads
D farads
The capacity of a storage battery is measured in what units? A volts B ampere-hours C farads D amps
B ampere-hours
What is the unit of measure for electrical power? A ampere B kilovolt C watt D farad
C watt
Electrical wire in general, when used aboard vessels must meet minimum requirements. Which of the following statements is/are correct?
(a) Wire need not be in an enclosure nor component insulated?
(b) Wire must be of the stranded copper type.
(c) Each wire must be 14 AWG or larger, regardless of locations and use.
(d) Wire must be of the solid copper type.
(b) Wire must be of the stranded copper type.
According to 46 CFR, Subchapter J (Electrical Engineering), when considering replacement, instrument and control wiring in a switchboard is to be of what minimum size?
(a) 12 AWG
(b) 14 AWG
(c) 16 AWG
(d) 18 AWG
(b) 14 AWG
The 24 volt DC bus on the emergency switchboard is used to supply power to what system or equipment?
(a) main lighting system
(b) general alarm and vital communication systems
(c) propulsion engine lube oil pump motors
(d) steering gear power unit motors
(b) general alarm and vital communication systems
When the electrolyte level of a lead-acid storage battery has decreased due to normal evaporation, how is a normal the level re-established?
A adding distilled water only
B adding sulfuric acid only
C adding a weak solution of sulfuric acid and distilled water
D adding a strong solution of sulfuric acid and distilled water
A adding distilled water only
What is the most common type of AC service generator found aboard ship in terms of armature and field types?
(a) stationary electromagnetic field, oscillatory armature type
(b) stationary armature, rotating electromagnetic field type
(c) stationary armature, oscillatory electromagnet field type
(d) stationary electromagnetic field, rotating armature type
(b) stationary armature, rotating electromagnetic field type
Which of the following statements represents the FIRST step in seating new brushes on slip rings?
(a) Press the brushes against the slip ring with a wood block.
(b) Apply seating compound under the brushes and run at no load for 2 hours.
(c) Increase brush pressure and run at no load for 3 to 4 hours.
(d) Lay sandpaper between the brush and the slip ring and slide the sandpaper back and forth under the brush.
(d) Lay sandpaper between the brush and the slip ring and slide the sandpaper back and forth under the brush.
Which of the following physical characteristics does a three-phase wound-rotor induction motor possess that a squirrel cage induction motor does not?
(a) Slip rings
(b) A centrifugal switch
(c) Compensating windings
(d) A commutator
(a) Slip rings
What is the correct name for the device used in an electrical circuit to change alternating current to direct current?
(a) rectifier
(b) shunt
(c) current transformer
(d) condenser
(a) rectifier
How is the main propeller shaft rotation of a rectified DC diesel-electric drive normally reversed?
(a) reversing the field polarity in the DC motor
(b) reversing the diesel engine rotation
(c) reversing the field polarity in the AC generator
(d) reversing the interpoles
(a) reversing the field polarity in the DC motor
[In DC motors, the magnets are stationary. In order to reverse direction you need to reverse the polarity.]
How is the reversal of an AC, three-phase, induction motor accomplished?
A changing all three motor leads
B reversing the position of the slip rings
C interchanging any two of the three line leads
D interchanging any two brushes
C interchanging any two of the three line leads
In the diagram of the switchboard shown in the illustration, if one of the turbines should fail due to a throttle trip, what will happen? EL-0003
(a) device labeled ‘BKR’ for that alternator should automatically open because of the reverse power relay
(b) emergency generator should automatically start and be placed on line to supply emergency load centers
(c) device labeled ‘EXC’ will drive the alternator
(d) operator must open all the devices labeled ‘BKRS’ to reduce the load on the remaining turbo-
alternator
(a) device labeled ‘BKR’ for that alternator should automatically open because of the reverse power relay
[BKR = circuit breaker]
In the illustrated switchboard, if both generators were operating in parallel and the kilowatt meter of panel 3 indicated a significantly higher value than the kilowatt meter on panel 1, which of the following procedures should you follow to balance the load? EL-0003
A Increase the governor speed setting in panel 1 and decrease the governor speed setting on panel 3
B Increase the governor speed setting in panel 3 and decrease the governor speed setting on panel 1
C Increase the setting of the voltage regulator in panel 3 and decrease the voltage regulator setting on panel 1
D Increase the setting of the voltage regulator in panel 3 and decrease the governor setting on panel 1
A Increase the governor speed setting in panel 1 and decrease the governor speed setting on panel 3
- Adjust the governors to balance power (kw).
- Adjust the voltage regulators to balance voltages.
If the cooling water system is isolated for repairs, but it is still desirable to run the alternator pictured in figure “A” of the illustration, what must be done? Illustration EL-0037
(a) The emergency air inlet panel and air outlet doors must remain closed, which requires the alternator to be run only at reduced loads.
(b) The emergency air inlet panel and air outlet doors must be opened and only then can the alternator be run, but at reduced load.
(c) The alternator may not be run without cooling water under any circumstances.
(d) The emergency air inlet panel and air outlet doors must be opened, but in doing so allows the
alternator to be run at rated load.
(b) The emergency air inlet panel and air outlet doors must be opened and only then can the alternator be run, but at reduced load.
Assuming the alternator shown in figure “A” of the illustration is equipped with a diode plate as configured in figure “D”, what is the purpose of the diode plate? Illustration EL-0037
(a) It inverts exciter armature DC to AC for rotating main field excitation, but does not eliminate the need for brushes. .
(b) It rectifies exciter armature AC to DC for rotating main field excitation, but does not eliminate the need for brushes..
(c) It rectifies exciter armature AC to DC for rotating main field excitation and eliminates the need for brushes.
(d) It inverts exciter armature DC to AC for rotating main field excitation and eliminates the need for brushes.
(c) It rectifies exciter armature AC to DC for rotating main field excitation and eliminates the need for brushes.
- Converts AC to DC
- Eliminates need for brushes
In a three-phase, squirrel-cage type, and induction motor, how is the primary rotating magnetic field established?
(a) laminated steel core and aluminum conductors in the rotor
(b) current induced in the rotor windings
(c) interaction of the magnetic field caused by the induced current in the squirrel-cage bars with
the magnetic field of the stator
(d) application of a three-phase voltage supply to the stator windings
(d) application of a three-phase voltage supply to the stator windings
How is the speed of a squirrel-cage induction motor determined?
(a) rotor conducting bars resistance
(b) number of stator poles
(c) diameter of the stator
(d) rotor winding resistance
(b) number of stator poles
What is the most practical method of controlling the RPM of a multi-speed AC motor operating at a constant frequency?
(a) change the number of operating poles
(b) change the input voltage
(c) change the power factor
(d) change the number of brushes
(a) change the number of operating poles
For what purpose is the variable resistance placed in the rotor circuit of a wound-rotor induction motor provided?
(a) frequency control
(b) voltage control
(c) torque control
(d) speed control
(d) speed control
What devices maintains equal power factors on paralleled AC generators automatically?
(a) voltage regulators
(b) reverse current relays
(c) reverse power relays
(d) governor speed control switches
(a) voltage regulators
Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency?
(a) A four-pole induction motor under no load.
(b) A four-pole synchronous motor under normal load.
(c) A six-pole induction motor under full load.
(d) A six-pole synchronous motor under normal load.
(b) A four-pole synchronous motor under normal load.
What is the main function in the use of a capacitor for starting a single phase motor?
(a) Reduce radio interference
(b) Prolong the life of the starting contacts
(c) Split the phase to create greater starting torque
(d) Reduce the phase angle
(c) Split the phase to create greater starting torque
What is the main purpose of the auxiliary winding on a split-phase, single-phase motor?
(a) keep the motor running in the event the main winding should fail
(b) provide starting torque
(c) increase the starting current
(d) limit the starting voltage
(b) provide starting torque
What would be the synchronous speed of an eight-pole three-phase squirrel-cage induction motor operating at 60 Hz?
(a) 875 rpm
(b) 900 rpm
(c) 1725 rpm
(d) 1800 rpm
(b) 900 rpm
RPM = [120 x freq] / no. of poles RPM = [120 x 60] / 8 = 900
Which type of AC single-phase motor will also operate on direct current?
(a) Series-wound
(b) Repulsion-start
(c) Shaded-pole
(d) Split-phase
(a) Series-wound
What type of rotor is most commonly used in the split-phase family of single-phase motors?
(a) Drum
(b) Squirrel-cage
(c) Salient pole
(d) Wound-rotor
(b) Squirrel-cage
How is the difference between the synchronous speed of a three phase induction motor and its operating speed correctly expressed?
(a) slip
(b) a percent of full load speed
(c) deviation
(d) a decimal fraction of full load speed
(a) slip
Regarding an induction motor, what does the power developed by the rotor automatically adjust itself to?
(a) speed required to drive the load
(b) torque developed by the rotating field
(c) power required to drive the load
(d) current flow in the motor stator
(c) power required to drive the load
Which of the illustrated motors has a totally enclosed, fan-cooled (TEFC) motor enclosure? Illustration EL-0001
(a) A
(b) C
(c) D
(d) B
(a) A
Which of the illustrated motors has an open motor enclosure? EL-0001
(a) A
(b) B
(c) C
(d) D
(b) B
Which of the illustrated motors has an open, drip-proof (ODP) motor enclosure? EL- 0001
(a) A
(b) B
(c) C
(d) D
(c) C
With respect to electrical enclosure types, how may an electric motor be designed and constructed?
(a) overload proof
(b) ground proof
(c) explosion proof
(d) short proof
(c) explosion proof
What is the primary means by which the motor branch circuit is protected from a short-circuited motor? EL-0004
A The thermal overload relay (OL)
B The secondary side control circuit fuses (FU6 and FU7)
C The primary side control circuit fuses (FU4 and FU5)
D The fused disconnect switch (Q1) fuses (FU1, FU2, and FU3)
D The fused disconnect switch (Q1) fuses (FU1, FU2, and FU3)
Impressed current cathodic hull protection systems are commonly used on modern vessels. What are these systems designed to replace or reduce?
(a) electroplating of the hull
(b) vacuum tube degaussing systems
(c) sacrificial zinc anodes
(d) repeated painting of the hull
(c) sacrificial zinc anodes
[Ref: EL-0090, cathodic protection system to interrupt electrolysis.]
As shown in the illustrated devices and symbols, which of the devices represents an open general purpose relay? Illustration EL-0005
(a) D
(b) C
(c) A
(d) B
(c) A
As shown in the illustrated devices and symbols, which of the symbols shown in the illustration represents a standard normally closed relay contact? EL-0005
(a) E
(b) F
(c) I
(d) K
(b) F
E: normally open
F: normally closed
G: coils
H, I, J, K: time to open/close
What will be the resulting current when a voltage of 110 VDC is applied to a resistance of 32 ohms in figure “A” of the illustrated circuit when the switch is closed? Illustration EL-0018
(a) 142 amps
(b) .29 amps
(c) 9.31 amps
(d) 3.44 amps
(d) 3.44 amps
I = E / R I = 110 / 32
What will be the resulting current when a voltage of 115 VDC is applied to a resistance of 12 ohms in figure “A” of the illustrated circuit with the switch closed? Illustration EL-0018
(a) 1.24 amps
(b) 127 amps
(c) 9.58 amps
(d) 104.34 amps
(c) 9.58 amps
I = E / R I = 115 / 12
What will be the resulting current when a voltage of 442.7 VDC is applied to a resistance of 1.25 ohms in figure “A” of the illustrated circuit when the switch is closed? Illustration EL-0018
(a) 35.32 amps
(b) 28.25 amps
(c) 443.62 amps
(d) 354.16 amps
(d) 354.16 amps
I = E / R I = 442.7 / 1.25
What is the unit of measure for resistance as well as impedance?
ohms
After a black out onboard and once ships power has been restored, the engine room supply fans must be started manually. What characteristic of the electrical circuit for the supply fans cause this requirement?
(a) The thermal overload has tripped and must be reset.
(b) The circuit for the supply fan is wired for low voltage release.
(c) The main breaker for the supply fan on the switchboard has tripped and must be reset
manually.
(d) The circuit for the supply fan is wired for low voltage protection.
(d) The circuit for the supply fan is wired for low voltage protection.
Compared to conventional alternators, brushless alternators are designed to operate without the use of what?
(a) voltage regulators
(b) rectifiers
(c) slip rings and commutators
(d) exciters
(c) slip rings and commutators
Refer to figure “A” representing an electric oven as shown in the illustration. With the oven turned on, the power available indicator light is off, the oven on indicator light is off, and only elements “6” and “7” appear to be producing heat. Which fuse is blown? (EL-0041)
(a) L1 10A line fuse is blown
(b) L2 10A line fuse is blown
(c) L3 10A line fuse is blown
(d) L1 1A control fuse is blown
(a) L1 10A line fuse is blown
As shown in figures “A” and “B” of the illustration, what happens when the “man-stop-auto” switch is placed in the “man” position? EL-0042
A If the disconnect switch is closed, the potable water pump will start and run continuously regardless of the pressure.
B Even with the disconnect switch open, the potable water pump will start and run continuously regardless of the pressure.
C If the disconnect switch is closed, the potable water pump will start and cycle on and off by the action of the pressure switch.
D Even with the motor experiencing overloads, the potable water pump will start and run continuously without tripping out on overload.
A If the disconnect switch is closed, the potable water pump will start and run continuously regardless of the pressure.
[In “auto” position, the pressure switch opens and closes to cycle the pump off and on as needed.]
Which of the diagrams shown in the illustration depicts the proper method of aligning brushes on a commutator for a DC machine? Illustration EL-0057
(a) A
(b) B
(c) C
(d) D
(c) C
[Brushes must be paired +/-, and aligned in an offset pattern.]
In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by what means?
(a) a hand operated band brake
(b) a manual override switch
(c) the weight of the load on the boom
(d) a spring set brake
(d) a spring set brake
As shown in the illustration, by what means are all the ‘MS’ contacts are opened and closed? EL-0073
(a) operating coils
(b) magnets
(c) solenoid switches
(d) manual operation of the master switches
(d) manual operation of the master switches
For the purposes of high voltage marine practice, what is the threshold voltage where all voltages below this value are considered low voltage?
(a) 1.0 kV
(b) 3.3 kV
(c) 6.6 kV
(d) 11 kV
(a) 1.0 kV
What is a disadvantage to the use of high voltage systems onboard ship?
(a) Reduced overall size of electrical power equipment
(b) Less current draw than with low voltage systems
(c) Necessary adherence to stringent safety procedures
(d) Reduced overall weight of electrical power equipment
(c) Necessary adherence to stringent safety procedures
Some shipboard high voltage systems have the neutral point of the generators bonded to the ship’s hull with a neutral grounding resistor. What is the purpose of this resistor?
(a) To completely eliminate ground fault current
(b) To maximize the magnitude of the ground fault current
(c) To prevent nuisance ground fault trips
(d) To minimize the magnitude of the ground fault current
(d) To minimize the magnitude of the ground fault current
Which statement is TRUE concerning electric propulsion drives?
(a) The propeller speed and direction of rotation are easily controllable.
(b) Lower transmission losses compared to other types of propulsion drives.
(c) Inability to be utilized as a source of ships service power.
(d) Lack of flexibility of arrangement between the prime mover and motor.
(a) The propeller speed and direction of rotation are easily controllable.
An electric propulsion drive system in which the propulsion generator supplies power to both the propulsion motor and ship service loads is referred to as what type of system?
(a) a multi-purpose system
(b) a dedicated system
(c) an integrated system
(d) a composite system
(c) an integrated system
What is one major advantage of a diesel electric propulsion plant?
(a) less maintenance
(b) lower fuel consumption
(c) excellent maneuverability
(d) low cost and weight
(c) excellent maneuverability
To facilitate communication between the wheelhouse and the steering gear room in a steering emergency where no external source of power is required, what means of two-way communication would be provided?
(a) Two-way portable radios
(b) Sound-powered telephone system
(c) Ship-service telephone system
(d) Emergency loudspeaker system
(b) Sound-powered telephone system
The electrical energy necessary to power a sound-powered telephone’s small vibrating bell is obtained from what power source?
(a) the emergency batteries for the general alarm
(b) normal 115 volt DC supplies
(c) the emergency switchboard
(d) each station’s hand-cranked generator
(d) each station’s hand-cranked generator
Referring to the sound-powered telephone circuit shown in the illustration, in what component are the sound-powered transmitter and receiver units located? (EL-0093)
(a) A
(b) B
(c) C
(d) D
(a) A
EL-0093 components: A) handset/receiver B) hand-cranked generator C) bell D) station selector switch
What is another name for the control mode used in a process control system that uses two-point control?
(a) Integral control
(b) Derivative control
(c) Proportional control
(d) On-off control
(d) On-off control
What process control system control mode is most likely to have steady-state error (also known as offset or residual error)?
(a) Proportional mode
(b) Proportional + Derivative mode
(c) Proportional + Integral + Derivative mode
(d) Proportional + Integral mode
(a) Proportional mode
In a closed-loop process control system, what is meant by the proportional mode of control?
(a) It is a control mode that produces a control action that is proportional to the gain.
(b) It is a control mode that produces a control action that is proportional to the rate at which the
error is changing.
(c) It is a control mode that produces a control action that is proportional to the accumulation of
error over time.
(d) It is a control mode that produces a control action that is proportional to the error.
(d) It is a control mode that produces a control action that is proportional to the error.
When tuning a Proportional, Integral, Derivative (PID) controller/loop, one should know/understand the influence of each action component on the loop. Which description of a component is correct?
(a) Integral - component in which the input is proportional to the output.
(b) Proportional - component in which there is a linear relationship between set point and input.
(c) Derivative - component in which the input is proportional to the rate of change of the output.
(d) Proportional - component in which there is a linear relationship between output and input.
(d) Proportional - component in which there is a linear relationship between output and input.
Refer to figures "1" and "2" of the basic synchronous transmission system shown in the illustration. Figure "1" shows a properly connected system where the receiver TR remains in correspondence with the transmitter TX. In figure "2", although properly zeroed, the receiver goes out of correspondence with the transmitter due to improper connections resulting in reverse torque direction. Which connection error results in this behavior? Illustration EL-0149 (A) A (B) B (C) C (D) D
(A) A
Which of the following figures shown in the illustration represents incandescent lighting? (EL-0122)
(a) A
(b) B
(c) C
(d) D
(a) A
B: high pressure
C: low pressure, mercury
D: high pressure
Referring to figure “1” of the illustration, what type of logic gate is symbolized? (EL- 0035)
(a) NOR gate
(b) XOR gate
(c) AND gate
(d) OR gate
(d) OR gate
Referring to figure “2” of the illustration, what type of logic gate is symbolized? (EL- 0035)
(a) OR gate
(b) XOR gate
(c) NOR gate
(d) AND gate
(c) NOR gate
Referring to figure “3” of the illustration, what type of logic gate is symbolized? (EL- 0035)
(a) AND gate
(b) XOR gate
(c) NOR gate
(d) OR gate
(a) AND gate
Referring to figure “4” of the illustration, what type of logic gate is symbolized? (EL- 0035)
(a) NOR gate
(b) AND gate
(c) NAND gate
(d) XOR gate
(c) NAND gate
Referring to figure “5” of the illustration, what type of logic gate is symbolized? (EL- 0035)
(a) XOR gate
(b) NOR gate
(c) AND gate
(d) OR gate
(a) XOR gate
Concerning the illustrated motor controller circuit, where is the location of the motor “run” indicator light? EL-0004
(a) At the local control station.
(b) At the remote control station.
(c) There is no motor “run” light. It is, instead, a motor “stopped” light.
(d) At the motor.
(b) At the remote control station.
As shown in the illustrated combination starter, what statement is true? EL-0004
A The primary function of the circuit breaker is for motor overload protection, as well as a means of disconnect.
B The control circuit operating voltage is the same as the motor operating voltage.
C The control circuit operating voltage is lower than the motor operating voltage.
D The motor overload relay resets automatically upon overload.
C The control circuit operating voltage is lower than the motor operating voltage.
[Note the transformer, T1.]
As shown in the illustrated combination starter, what statement is true? EL-0004
A The primary function of the circuit breaker is for motor overload protection, as well as a means of disconnect.
B The control circuit operating voltage is the same as the motor operating voltage.
C The motor overload relay must be manually reset upon overload.
D The motor overload relay resets automatically upon overload.
C The motor overload relay must be manually reset upon overload.
As shown in figure "B" of the illustration, what does the M-G set's three-phase drive motor mechanically drive? EL-0101 A the DC generator armature B the DC generator field C the DC motor armature D the field rectifier
A the DC generator armature
What is the name of the DC motor speed control method utilized as shown in figure “B” of the illustration? Illustration EL-0101
(a) Burmeister-Wain
(b) Atlas-Copco
(c) Ward-Leonard
(d) Sperry-Rand
(c) Ward-Leonard
As shown in all four diagrams included in the illustration, what type of logic circuit is represented? (EL-0227)
(a) NOR gate
(b) OR gate
(c) AND gate
(d) NAND gate
(b) OR gate
In general, what type of starter would be used to connect polyphase induction motors to full line voltage at the instant of start-up?
(a) auto-transformer starters
(b) across-the-line starters
(c) compensator starters
(d) primary-resistor starters
(b) across-the-line starters
[Full voltage starting: across-the-line.]
An across-the-line starter is typically used for which of the following applications?
(a) Reduced-current starting of large motors
(b) Full-voltage starting of motors
(c) Low torque starting of small motors
(d) Low resistance starting of DC motors
(b) Full-voltage starting of motors
With what kind of starting equipment are most three-phase induction motors of five horsepower or less started?
(a) across-the-line starters
(b) resistor starters
(c) autotransformer starters
(d) reactor starters
(a) across-the-line starters
What is a common type of protective covering used on electrical conductors?
(a) plain paper
(b) silver sheathing
(c) rubber or plastic
(d) Babbitt sheathing
(c) rubber or plastic
In the illustrated motor controller, what do the contacts across terminals “3” and “4” of the control circuit represent? Illustration EL-0017
(a) thermal overload heater
(b) normally-closed overload relay contact
(c) magnetic overload coil
(d) normally-open overload relay contact
(b) normally-closed overload relay contact
As shown in the illustration, which of the following conditions will occur as a result of a momentary loss of power? Illustration EL-0017
(a) the “off-run” selector switch will re-open, necessitating a manual restarting of the motor.
(b) The normally-closed OL relay contacts will open requiring a manual reset, necessitating a
manual restarting of the motor.
(c) The motor will automatically restart when power is restored.
(d) The disconnect switch (DS) will re-open, necessitating a manual restarting of the motor.
(c) The motor will automatically restart when power is restored.
As shown in the illustration, assuming power is available at the control circuit, which listed action will occur FIRST when the “off-run” switch is placed in the “run” position? Illustration EL-0017
(a) The disconnect switch (DS) contacts close.
(b) The “OL” relay contacts close.
(c) The contactor coil “M” energizes.
(d) The main contacts (3) “M” close, connecting the motor to line..
(c) The contactor coil “M” energizes.
With what device is the simplest method of controlling the terminal voltage of compound-wound DC generator?
(a) carbon pile regulator in series with the load
(b) hand-operated field rheostat connected in series with the shunt field circuit
(c) balance coil diverting neutral current through the shunt field
(d) separate exciter in a series with the shunt field
(b) hand-operated field rheostat connected in series with the shunt field circuit
[Control the voltage by adjusting the field.]
Which of the following statements is true concerning the operation of two alternators in parallel?
(a) Both alternator governors must be set with the same amount of speed droop.
(b) The number of field poles must be the same on each alternator.
(c) The cycles per second of each alternator are the same.
(d) The load must always be divided equally between alternators.
(c) The cycles per second of each alternator are the same.
What device is used so that the kilowatt load sharing can be adjusted on paralleled generators?
(a) governor control
(b) hand tachometer
(c) automatic voltage regulators
(d) field rheostat
(a) governor control
Prior to closing the circuit breaker when paralleling two DC generators, what must you be certain of?
(a) voltage of the incoming machine is at or slightly above the bus voltage
(b) synchroscope needle is revolving slowly in the ‘fast’ direction
(c) frequency of the incoming machine is slightly higher than the bus frequency
(d) current from the incoming machine is the same as the bus current
(a) voltage of the incoming machine is at or slightly above the bus voltage
As shown in figure “1” of the illustration, a correctly connected synchronous transmission causes the receiver to be in correspondence with the transmitter. If the receiver is out of correspondence, 180 degrees out of zero, but the torque direction is correct as shown in figure “2”, what figure shows the incorrect connections responsible for this condition? Illustration EL-0150
(a) A
(b) C
(c) B
(d) D
(c) B
The nominal voltage of one cell of a wet cell nickel-cadmium battery is approximately how many volts?
(a) 1.2 volts
(b) 1.5 volts
(c) 2.0 volts
(d) 3.0 volts
(a) 1.2 volts
