Book 8 Flashcards
Which unit is used to measure the magnitude of an electromotive force?
a.
Amps
b.
Electrons
c.
Ohms
d.
Volts
Volts
When using the Left Hand Rule for Motors, the index finger represents:
Select one:
a.
Magnetic flux direction, for generators
b.
Conductor motion direction, for motors
c.
Flux direction, for motors
d.
Direction of current flow, for motors.
Flux direction, for motors
Shunt wound DC motors are used where speed must remain constant regardless of load, such as on:
Select one:
a.
Automobile starters
b.
Elevators
c.
Lathes
d.
Traction engines
Feedback
Lathes
Low voltages include all voltages between _____ V.
Select one:
a.
0 and 30
b.
30 and 220
c.
30 and 750
d.
100 and 750
30 and 750
To transfer the power to or from the rotor of alternators, ____________ are used.
Select one:
a.
Field poles
b.
Commutators
c.
Slip rings
d.
Hard-wired connections
Slip rings
The direction of the _____ on the conductor may be determined using the Left Hand Rule for Motors.
Select one:
a.
force
b.
polarity
c.
resistance
d.
voltage
force
The instrument used to measure electrical power used in a period of time, is the:
Select one:
a.
Kilowatt hour meter
b.
Voltmeter
c.
Ohmmeter
d.
Milli-ammeter
Kilowatt hour meter
If the power dissipated by a resistor is 1.2 kW when supplied with 110 V, the amperage will be _____ A.
Select one:
a.
91.666
b.
19.006
c.
10.91
d.
132
10.91
The basic unit of electrical power is the watt, which is the product of:
Select one:
a.
Volts x resistance.
b.
Volts x ohms.
c.
Volts x amperes.
d.
Ohms x amperes.
Volts x amperes.
What can be used so that one side of the loop is always connected to the same side of the external circuit?
a.
A commutator
b.
Brushes
c.
Slip rings
d.
An armature
Slip rings
Transformers:
Select one:
a.
Step up or down AC voltage
b.
Transform AC voltage to DC voltage
c.
Rectify DC voltage to AC voltage
d.
Step up DC voltage
Step up or down AC voltage
The black demand pointer of a kilowatt hour meter:
Select one:
a.
Moves the red pointer
b.
Reads the current demand
c.
Indicates the maximum voltage being drawn
d.
Must be manually reset
Must be manually reset
Faraday discovered:
Select one:
a.
The Right Hand Rule for conductors
b.
That a conductor will have a voltage induced if it moves through a magnetic field
c.
The Left Hand Rule for motors
d.
The Left Hand Rule for generators
The correct answer is: That a conductor will have a voltage induced if it moves through a magnetic field
Three resistances of 20, 50 and 80 Ω make up a series circuit. The supply voltage is 400 V. The current flowing would be:
Select one:
a.
2.67 A
b.
8 A
c.
5 A
d.
0.375 A
The correct answer is: 2.67 A
Which of the following is NOT safe practice when operating a safety switch?
a.
Stand on the hinged side of the switch door
b.
Face the switch
c.
Walk away from the switch as soon as the switch makes contact
d.
Operate the switch with the non-dominant hand
The correct answer is: Face the switch
Extra low voltages include all voltages below _____ V.
Select one:
a.
30
b.
50
c.
110
d.
220
Feedback
The correct answer is: 30
A material that transfers electric charge is called:
Select one:
a.
An insulator
b.
A conductor
c.
A circuit
d.
A wire
Feedback
The correct answer is: A conductor
Tie breakers are used to:
Select one:
a.
Allow the interconnection of two power sources without placing them in parallel
b.
Break the circuit in case of overload
c.
Protect the transformer from the power source
d.
Protect the plant service bus from the power source
The correct answer is: Allow the interconnection of two power sources without placing them in parallel
The total circuit resistance is less than a value of any individual resistor:
Select one:
a.
When voltage is decreased
b.
When the resistors are wired in parallel
c.
If the amperage is increased
d.
When the resistors are wired in series
The correct answer is: When the resistors are wired in parallel
The total number of lines of ________ in a magnetic field determine(s) the value or magnitude of the flux.
a.
Force
b.
Current
c.
Flux
d.
Volts
Force
___________ are used on motors and generators to produce the strong magnetic field required by these machines.
Select one:
a.
Insulated wires
b.
Transformers
c.
Rheostats
d.
Pole pieces
Pole pieces
Three resistors of 20, 60 and 120 Ω are connected in parallel with a current flow of 60 A. The applied voltage will be _____ V.
Select one:
a.
7200
b.
800
c.
13.33
d.
0.33
800
The right hand rule for generators is used to:
Select one:
a.
Indicate the speed of a rotor
b.
Determine direction of induced current flow
c.
Determine the frequency of an alternator
d.
Determine magnetic flux rotation
Determine direction of induced current flow
The strength of the magnetic field produced in a shunt wound generator:
Select one:
a.
Is weak
b.
Is fairly constant
c.
Is regulated by an external AC supply
d.
Increases with generator load
Is fairly constant
A triple pole single throw switch is one that:
Select one:
a.
Opens and closes three wires of an electrical circuit
b.
Has three magnetic poles
c.
Is used for three phase circuits only
d.
Requires three toggles
Opens and closes three wires of an electrical circuit
Which governing body assigns the frame numbers that designate specific external dimensions to motors?
a.
NFPA 70 National Electrical Code
b.
International Electrical Commission (IEC)
c.
CSA C22.1 Canadian Electrical Code (CEC)
d.
National Electric Manufacturers Association (NEMA)
National Electric Manufacturers Association (NEMA)
Electromotive force:
Select one:
a.
Moves electrons through a conductor
b.
Is able to move ohms through a resistance
c.
Is increased by a resistor
d.
Is increased by a voltage drop
Moves electrons through a conductor
The opposition that a device or material offers to the flow of electric current is known as:
Select one:
a.
resistance
b.
conductance
c.
voltage drop
d.
insulation
resistance
If the applied voltage in a circuit is 120 V and the current flow is 3 A the resistance of this circuit is:
Select one:
a.
40 W
b.
0.025 Ω
c.
360 Ω
d.
40 Ω
40 Ω
The main components of a DC machine are the non-moving assembly, called the _____, and the rotor, which is also called an armature.
Select one:
a.
Wiring
b.
Stator
c.
Rheostat
d.
Generator
Stator
Electrons are negatively charged particles:
Select one:
a.
Orbiting about the nucleus of an atom
b.
Firmly attached to the neutrons of an atom
c.
That can easily flow through insulators
d.
That seek open circuits
Orbiting about the nucleus of an atom
Which component is responsible for electrical distribution and from the distribution network?
a.
Branch circuits
b.
Transformers
c.
Feeders
d.
Motor control center
Feeders
When reading the dials of a kilowatt hour meter, read:
Select one:
a.
Them in the sequence shown by the letters under each
b.
Them from left to right
c.
The ones that rotate clockwise first
d.
Them from right to left
Them from right to left
Alternators are constructed with slip rings made of brass or:
Select one:
a.
Copper
b.
Carbon
c.
Mica
d.
Steel
Steel
In a series wound DC generator:
Select one:
a.
Brushes change DC to AC for the armature
b.
The shunt winding is connected taps in before the series winding
c.
Load current passes through the field windings
d.
The shunt winding is connected after the series winding
Load current passes through the field windings
Apparent power is the
Select one:
a.
kW of power consumed
b.
VA supplied to a reactive AC circuit
c.
Power due to resistance in a circuit
d.
Power recorded by a kWh meter.
VA supplied to a reactive AC circuit
Which of the following is not a type of electrical diagram?
a.
Connection or wiring diagram
b.
Electrical flow diagram
c.
Riser diagram
d.
Schematic or elementary diagram
Electrical flow diagram
The voltage induced in the secondary windings of the transformer, is _____ the turns ratio of the transformer.
Select one:
a.
proportional to
b.
reversed to
c.
opposed by
d.
inversely proportional to
proportional to
What happens as conductors move parallel to the magnetic line of force?
a.
Maximum EMF is generated
b.
The right-hand rule must be followed
c.
The left-hand rule must be followed
d.
No EMF is generated
No EMF is generated
Which meter is used to test the quality of a conductor’s insulation?
a.
Voltmeter
b.
Megohmmeters
c.
Ammeter
d.
Ohmmeter
Megohmmeters
_____ is a unit of electromotive force.
Select one:
a.
The Ampere
b.
The Ohm
c.
The Watt
d.
The Volt
The Volt
Which equipment converts AC power to DC power?
a.
Transformer
b.
Inverter
c.
Transfer switch
d.
Rectifier
Rectifier
What is the electromotive force developed by an alternator proportional to?
a.
Conductor speed
b.
Cycles produced at the alternator terminals
c.
Number of poles
d.
Number of phases
Conductor speed
Permanent magnets are used for:
Select one:
a.
Shunt motors
b.
Series motors
c.
Small portable alternators
d.
Induction motors
Small portable alternators
When current flows in a conductor:
Select one:
a.
AC voltage is generated
b.
The conductor develops north and south poles
c.
A circular magnetic field is set up around the conductor
d.
All magnetic forces are dissipated
A circular magnetic field is set up around the conductor
The stator of an alternator is built of _____ mounted in a frame.
Select one:
a.
Copper alloys
b.
Laminated steel sheets
c.
Carbon ring
d.
Armature conductors
e.
Non-metallic materials
Laminated steel sheets
A clamp-on ammeter measures current flow by using:
Select one:
a.
Shunting current through a milli-ammeter
b.
Differential current flow between two conductors
c.
A basic transformer principle
d.
A portion of circuit resistance
A basic transformer principle
Which maintenance activity requires transformer to be de-energized?
a.
Using thermal imaging cameras
b.
Taking transformer readings
c.
Removing any panel or cover
d.
Checking containments
Feedback
Removing any panel or cover
When AC action causes a back EMF in the same coil of wire, it is termed:
Select one:
a.
Self inductance
b.
Capacitance
c.
Mutual inductance
d.
Electromagnetic induction
Self inductance
The voltage drop across a 20 Ω resistor with 10 A flowing would be _____ V.
Select one:
a.
2
b.
0.5
c.
200
d.
20
200
The basic unit of mechanical or electric power is the:
Select one:
a.
Volt
b.
Watt
c.
Ampere
d.
Ohm
Watt
The equivalent resistance of three resistances of 10, 25 and 50 Ω connected in parallel is _____ Ω.
Select one:
a.
0.16
b.
6.25
c.
18.75
d.
8.5
6.25
The load current has no effect on the field excitation of a:
Select one:
a.
Compound wound generator
b.
Series wound generator
c.
Shunt wound generator
d.
Separately excited generator
Separately excited generator
An instrument transformer used to measure voltage is called a:
Select one:
a.
Current transformer
b.
Step down transformer
c.
Potential transformer
d.
Auto-transformer
Potential transformer
Atoms that have greater than 3 electrons in the outer shell are:
Select one:
a.
Positively charged
b.
Good conductors
c.
Neutrally charged
d.
Poor conductors
Poor conductors
What power is dissipated by a resistor with a supply voltage of 120 V and a current of 8 A?
Select one:
a.
15 Ω
b.
15 W
c.
960 W
d.
96 kW
960 W
If a material provides resistance to magnetic flux, it is demonstrating:
Select one:
a.
Resistance
b.
Reluctance
c.
Impedance
d.
Repulsion
Reluctance
A compound wound DC generator has a combination of shunt and _____ characteristics, depending on the predominance of each type of winding.
Select one:
a.
Parallel
b.
Separately-excited
c.
Induction
d.
Series
Series
Which of the following is a requirement for synchronizing alternators?
Select one:
a.
Amperages must be equal
b.
Voltages must be out-of-phase
c.
Phase rotations must be leading by 120 degrees
d.
Frequencies must be equal
Frequencies must be equal
What is the correct reading off of this energy dial?
a.
1463
b.
3641
c.
4641
d.
1464
3641
An operating current transformer should never:
Select one:
a.
Be inspected until properly grounded
b.
Have its primary circuit opened
c.
Produce excessively high voltages
d.
Have its secondary circuit opened first
Have its secondary circuit opened first
Harmonic frequencies generate additional current within the transformer. What effect do these frequencies have?
a.
They tend to overheat and damage the transformer
b.
They have no effect on the transformer
c.
They tend to increase efficiency of the transformer
d.
They add to the total current generated
They tend to overheat and damage the transformer
The yoke that supports the main components of the DC machine is frequently made of:
Select one:
a.
Copper or brass
b.
Composite materials
c.
Steel or iron
d.
Aluminum
Steel or iron
An AC motor which will drop out of synchronism and simply trip when overloaded is the:
Select one:
a.
Slip-ring induction motor
b.
Induction motor
c.
Wound rotor induction motor
d.
Synchronous motor
Synchronous motor
Single-phase transformers:
Select one:
a.
Use two common forms of construction known as the core type and the shell type.
b.
High voltage coil is nearest the iron core.
c.
Use two common forms of construction known as the internal type and the external type.
d.
Are very low in efficiency.
Use two common forms of construction known as the core type and the shell type.
Ammeters are connected:
Select one:
a.
In parallel with the circuit
b.
In series with the circuit
c.
In parallel with the circuit to measure the resistance
d.
So that voltage will bypass the meter
In series with the circuit
Current transformers are:
Select one:
a.
Current step-up transformers
b.
K-type transformers
c.
High power factor transformers
d.
Voltage step-up transformers
Voltage step-up transformers
The field strength of an alternator can be adjusted by varying the amplitude of the DC power supply to the:
Select one:
a.
Rotating field
b.
Stator windings
c.
Rotating stator
d.
Pole pieces
Rotating field
Alternators must run at constant speed in order to maintain:
Select one:
a.
Current
b.
Power output
c.
Constant voltage
d.
Frequency
Frequency
The voltage produced in each phase of a three phase generator is displaced by _____ electrical degrees from the other phases:
Select one:
a.
120
b.
90
c.
60
d.
30
120
Watt meters measure:
Select one:
a.
Apparent power
b.
Power factor
c.
Resistance to current flow
d.
Active power
Active power
A voltmeter must ______________ electrical circuit.
Select one:
a.
Offer low resistance to the
b.
Offer no resistance to the
c.
Offer slight resistance to the
d.
Offer high resistance to the
Offer high resistance to the
A transformer works on the principle of:
Select one:
a.
Hysteresis
b.
Mutual induction
c.
Eddy currents
d.
Kirchhoff’s law
Mutual induction
The minimum voltage generated by a single loop DC generator occurs when the conductor is traveling, relative to the magnetic lines of force:
Select one:
a.
at an angle of 45°
b.
at an angle of 90°
c.
at an angle of 120°
d.
parallel to the lines of force
parallel to the lines of force
The best type of diagram for showing supply and distribution system is the _____ diagram.
Select one:
a.
Riser
b.
Single-line
c.
Connection
d.
Terminal and connection
Single-line
In an atom the electrons:
Select one:
a.
Orbit around each other
b.
Are repelled by the neutrons
c.
Are attracted to the protons
d.
Are large in size when compared to the protons
Are attracted to the protons
The voltage required to force a current of 15 A through a resistance of 5 Ω will be _____ V.
Select one:
a.
3
b.
7.5
c.
33
d.
75
75
Neglecting the efficiency of a 15 kW motor connected to a 400 V supply, the amperage will be _____ A.
Select one:
a.
26.667
b.
37.5
c.
0.0375
d.
3.75
37.5
Brush gear for DC machines have brushes made from carbon because
Select one:
a.
carbon is a good insulator
b.
carbon reduces the friction at the commutator
c.
carbon brushes are easy to manufacture
d.
they are inexpensive
carbon reduces the friction at the commutator
Clamp-on ammeter readings may be inaccurate if:
Select one:
a.
Jaws are dirty or misaligned
b.
Circuit voltage is too high
c.
Circuit resistance is too low
d.
Conductor insulation is too thick
Jaws are dirty or misaligned
A common use for a DC generator is:
Select one:
a.
Power supply for an elevator
b.
An automobile alternator
c.
Emergency power
d.
Power factor correction
Power supply for an elevator
A basic law of electricity is, unlike charge attract each other and like charges:
Select one:
a.
Repel each other
b.
Hold each other
c.
Attract each other
d.
Neutralize each other
Repel each other
Find the line voltage when three resistors of 20 Ω, 30 Ω, and 40 Ω are connected in parallel. The current passing through the 20 Ω resistance is 1.5 A. Also determine the line current.
a.
100 V, 9.23 A
b.
60 V, 6.25 A
c.
100 V, 18.46 A
d.
30 V, 3.25 A
30 V, 3.25 A
Transformers are often cooled by:
Select one:
a.
immersing the core in a refrigerant bath
b.
forced cooling with fans
c.
immersing the core in cooling water
d.
using windings with less insulation
forced cooling with fans
_____ current flow is from positive to negative.
Select one:
a.
Alternating
b.
Direct
c.
Conventional
d.
Electron
Conventional
The flow of electrons in a uniform direction is called:
Select one:
a.
Voltage drop
b.
Electric current flow
c.
Potential difference
d.
Electromotive flow
Electric current flow
An electrical distribution system is composed of service, feeders and:
Select one:
a.
Secondary circuits
b.
Primary circuits
c.
Branch circuits
d.
Trunk circuits
Feedback
Branch circuits
A typical extra low voltage device would be a:
Select one:
a.
Toaster
b.
Fluorescent light
c.
Door bell
d.
Step-down transformer
Door bell
Copper losses in a transformer are reduced by:
Select one:
a.
Using iron core laminations instead of copper
b.
Using larger diameter wire
c.
Reducing the primary voltage
d.
Increasing the secondary voltage
Using larger diameter wire
The purpose of having an upward movement of a switch handle to close the switch is:
Select one:
a.
To have the handle out of the way
b.
To meet the requirements of the electrical codes
c.
It indicates the condition of the circuit
d.
To prevent the switch from closing due to gravity
To prevent the switch from closing due to gravity
A closed electrical circuit will:
Select one:
a.
Close-off the flow of current
b.
Be series only
c.
Be parallel only
d.
Allow current to flow
Allow current to flow
Low voltage systems may have an actual voltage variation of plus or minus:
Select one:
a.
10%
b.
4%
c.
1.5%
d.
7.5%
4%
If a conductor is held stationary and a magnetic field is moved across it, it behaves according to
Select one:
a.
Motor action
b.
Electromagnetism
c.
Generator action
d.
Transformer action
Generator action
Because of environmental concerns, it is no longer permissible to add ____________ to transformer oil.
Select one:
a.
Anti-foaming substances
b.
Polyhlorinated biphenyls
c.
Freon
d.
Organic compounds
Polyhlorinated biphenyls
The voltmeter is placed:
Select one:
a.
In series with the ammeter
b.
In parallel with the circuit
c.
In series with the circuit
d.
Between the battery and the first resistance
In parallel with the circuit
Three-phase transformers have:
Select one:
a.
Three windings
b.
Two windings on the primary side and one on the secondary
c.
Six windings
d.
Nine windings
Six windings
For three-phase power, each conductor is _____ electrical degrees out of phase with the others.
Select one:
a.
30
b.
90
c.
120
d.
180
120
An electrical device that is designed to start and stop current flow is the:
Select one:
a.
Power supply
b.
Fuse
c.
Circuit breaker
d.
Switch
Switch
Current flow is:
Select one:
a.
Increases as the applied voltage increases
b.
Proportional to the resistance
c.
Unaffected by resistance
d.
Increases when applied voltage decreases
Increases as the applied voltage increases
If the line voltage ES is 120 V, what is the voltage drop across each resistor in a circuit that has a 15 Ω and a 25 Ω resistance connected in series?
a.
2 A
b.
1 A
c.
4 A
d.
3 A
3 A
