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WorksheetsTechnical/ Pre-board Exam/ March 03, 2023
Total questions: 50
Worksheet time: 25mins
Galvanized conduit has a finish exterior and interior of ____
Lead
Copper
Nickel
Zinc
Permeability is ____
The opposite of conductance
A measure of the ease with which magnetism passes through any substances
The total resistance to current flow
The liquid substance in a batterry
Which of the following is not true?
It is an electrical impossibility to have a circuit with only inductive reactance because the metallic wire has a resistance
The voltage of a circuit is the greatest effective difference of potential that exists between any two conductors of a circuit
The current is said to lag the voltage in a circuit that has only capacitive reactance
Power factor is the phase displacement of current and voltage in and AC circuit
A transformer has a primary voltage of 120 volts and a secondary voltage of 480 volts. If there are 40 turns on the primary, the secondary contains____.
10 turns
40 turns
120 turns
160 turns
To check voltage to ground, you would check from____.
The breaker to the cabinet
Hot to neutral
The breaker to the grounding terminal
All of these
The definition of ampacity is____.
The current-carrying capacity of conductors expressed in volt-amper
The current-carrying capacity expressed in amperes
The current-carrying capacity of conductors expressed in wattage
The current in amperes a conductor can carry continuously under the conditions of use without exceeding its temperature rating
Find the amperage of a 5kVa load on a 220-V 3 phase branch circuit?
13A
8.66A
12.7A
22A
An AC circuit has resistance of 4 ohms and a reactance of 3 ohms. What is the impedance?
7 ohms
5 ohms
12 ohms
8 ohms
If the allowable current in a copper bus bar is 1000 ampere per square inch of cross section, the width of a standard 1/4 bus bar design to carry 1500 ampere would be?
4 inches
6 inches
8 inches
2 inches
What relationship determines the efficiency of electrical equipment?
The power input divided by the output
The volt-amps x the wattage
The VA divided by the pf
The power output divided by the input
As the power factor of a circuit is increases____.
Reactive power is decreased
Active power is decreased
Reactive power is increased
Both active and reactive power are increased
How many kw hours are consumed by 25-60 watt light bulbs burning 5 hours in a 120V circuit?
1.5
180
7.5
75
An AC ammeter or voltmeter is calibrated to read RMS values; this means the meter is reading the____.
Maximum
Peak
Average
Effective
A 3 ohms, 6 ohms, 9 ohms and 12 ohms resistor are connected in series. The resistor that will consume the most power is the ____ohm.
3
6
9
12
Two switches in one box under one face-plate is called a____.
Double-pole switch
Two-gang switch
2-way switch
mistake
The current will lead the voltage when____.
Inductive reactance exceeds the capacitive reactance in the circuit
Reactance exceeds the resistance in the circuit
Resistance exceeds the reactance in the circuit
Capacitive reactance exceeds the inductive reactance in the circuit
In general, the most important point to watch in the operation of transformers is the____.
Core loss
Exciting current
Temperature
Primary voltage
For maximum safety the magnetic contactors used for reversing the direction of rotation of a motor should be?
Operated from independent sources
Electrically interlocked
Mechanically interlocked
Electrically and mechanically interlocked
An electron is ____.
A neutron
An orbiting particle
A proton
The smallest part of an atom with negative charge
If the current flow through a conductor is increased, the magnetic field around the conductor____.
Is unchanged
Becomes stronger
Collapses
Becomes weaker
If two equal resistance conductors are connected in parallel, the resistance of the two conductors is equal to?
The resistance of one conductor
Twice the resistance of one conductor
One-half the resistance of one conductor
The resistance of both conductors
An ammeter is connected____.
across the load
in series with the load
in series-parallel across the load
none of these
The primary and secondary windings of a transformer always have____.
A common magnetic circuit
The same size wire
Separate magnetic circuits
The same number of turns
A 10 pole AC generator is running at 600 rpm, what is the frequency of the generated voltage?
60 Hz
50 Hz
70 Hz
40 Hz
The field winding of a shunt motor has a resistance of 110 ohms and the voltage applied is 220 V. What is the amount of power expended in the field excitation?
330 W
220 W
440 W
500 W
Resistance offered by the active material of a cell?
Bulk resistance
Internal resistance
Absolute resistance
Specific resistance
To dissipate internal heat in a generator, it is built with?
Laminated core
Insulation
Special non-conductors
None of these
At absolute zero temperature a semi-conductor behaves as a?
Good conductor
Variable resistor
Good insulator
Super conductor
At absolute zero temperature a semi-conductor behaves as a?
Good conductor
Variable resistor
Good insulator
Super conductor
Circuit breakers shall be marked with a voltage rating no less than the nominal system voltage that is indicative of their capability to interrupt.
I. fault currents between phases
II. fault currents from the phase to ground
III. fault currents between the neutral and ground
I only
I & II only
II & III only
I, II or III
An oven takes 11 amperes at 220 volts. It is desiring to reduce the current 10 amperes. What resistance must connect in series?
2 ohms
22 ohms
20 ohms
5 ohms
A 10 mH inductor has a reactance of ____at 60 Hz?
0.377 ohms
3.77 ohms
37.7 ohms
7.37 ohms
A certain motor takes 350 amperes at 100 volts and have an output of 45 HP. What is the efficiency?
95.6 %
95.9 %
97.2 %
93.5 %
At no load the terminal voltage of an alternator is 530 volts at rated load, the voltage drops to 480 volts.
Calculate the percentage voltage regulation of the machine.
10.42 %
9.43 %
90.56 %
12.52 %
A series circuit has a resistance of 10 ohms and reactance of 5 ohms. What is the circuit power factor?
0.50
0.866
0.75
0.89
The voltage of a circuit is best defined as____?
the potential between two conductors
the greatest difference of potential between two conductors
the effective difference of potential between two conductors
the average RMS difference of potential between any two conductors
The unit of measure for electrical capacity is the____.
ohm
henry
farad
watt
How many 4-way switches are required to switch a light from three places?
one
two
three
four
Pure XL in a circuit will cause a ____ degree lag of the ampere curve to the voltage curve in an AC circuit.
90
120
180
240
The disadvantage of AC compared to DC would be____.
smaller conductors to transmit electrical energy
reduced cost transmission with high voltage transformers
less copper required with AC at higher voltages
cannot be used in electro-plating
Wound rotor and squirrel cage are two types of____motors.
synchronous
single-phase
induction
poly phase
In a multiple motor circuit there is feeder protection, branch-circuit protection and motor protection. If the feeder protection trips, the fault would be expected to be in____.
one of the motors
one of the branch-circuits
the feeder
one of the starters
Which of the following in not a factor in calculating the feeder conductor size?
ambient temperature
branch-circuit protection
voltage drop
demand factors
For voltage and current to be in phase____.
A. voltage and current appear at their zero and peak values at the same time
B. the circuit impedance has only resistance
C. neither a nor b
D. both a and b
Electro-magnetic devices usually have a____core.
aluminum
soft iron
hard iron
hard steel
The value of the resistor is 47 kilo ohms with 5% tolerance. Which of the following indicate the color bands combination?
yellow-green-red-gold
yellow-violet-red-gold
blue-yellow-orange-silver
yellow-violet-orange-gold
A parallel circuit is one that has,
All elements connected end to end
Same current flowing through all elements
All elements connected across the power supply so that removing one element does not stop the others from working
All elements placed side by side
This term means that the motor will stop when there is a supply voltage failure and the motor will restart automatically when the voltage is restored.
No voltage release
No voltage protection
No voltage control
All of these
Which of the following protection features a motor starter is not readily needed?
No voltage protection
Ground fault protection
Single phasing protection
Overload protection
Another name for a plugging switch.
Centrifugal switch
Zero speed switch
Break make switch
Rocker switch
