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WorksheetsELEX Pre-Board Exam 12
Total questions: 100
Worksheet time: 3hrs 20mins
Name
Class
Date
1.
An advantage of an electromagnet over a permanent magnet is that:
a)
An electromagnet can be switched on and off
b)
An electromagnet does not have specific polarity
c)
An electromagnet requires no power source
d)
Permanent magnets must always be cylindrical
2.
The quantity of magnetism retained by a magnetic material after withdrawal of the magnetized force is called
a)
Leftover magnetism
b)
Residual magnetism
c)
Hysteresis
d)
Coercivity
3.
Three resistors of 10, 15, and 20 Ω each are connected in parallel. What is the total conductance?
a)
0.217 S
b)
3.41 S
c)
4.62 S
d)
0.52 S
4.
What temperature in which the specific resistance of materials is usually measured?
a)
290 K
b)
300 K
c)
20°C
d)
0°C
5.
When one resistance in a series string is open, the
a)
current is maximum in the normal resistances
b)
current is zero in all of the resistances
c)
voltage is zero across the open resistance
d)
current increases in the voltage source
6.
The equivalent wye element of 3 equal resistors each equal to R and connected in delta is
a)
R
b)
3R/2
c)
R/3
d)
3R
7.
A lead storage battery is rated at 12 V. If the internal resistance is 0.01 Ω, what is the maximum power that can be delivered to the load?
a)
1,200 W
b)
7,200 W
c)
3,600 W
d)
1,800 W
8.
A simple circuit having a source of 7 nanovolts and a load of 3 kilo-mega ohms has a current equivalent to
a)
23.33 amperes
b)
2.333 attoamperes
c)
2.333 amperes
d)
2.333 deca amperes
9.
What happens to the flow of electrons in electronic circuit when the resistance is increased?
a)
The speed of flow will remain constant
b)
The flow become faster
c)
The flow will be decreased
d)
No flow will occur
10.
A circuit contains an inductor of 10 H in series with the capacitor of 0.001 F and operating at a frequency of 4 MHz. What is the net reactance or X in MΩ?
a)
2.4727
b)
2472.7
c)
247.27
d)
24.727
11.
What is the relationship between frequency and the value of R?
a)
R varies indirectly
b)
Frequency has no effect
c)
R varies directly
12.
Longest life cell capable of 20, 000 times charged-discharged cycle and could last 30 years or over
a)
Nickel-cadmium cell
b)
Lithium cell
c)
Nickel hydrogen
d)
Alkaline cell
13.
It is considered to be a negative charge of electricity?
a)
Atom
b)
Electron
c)
Neutron
d)
Proton
14.
Refers to a field surrounding electrons and protons at stationary period indicating a stored energy
a)
Magnetic field
b)
Electrostatic field
c)
Electron field
d)
Electrodynamic field
15.
The time required to complete one complete cycle of a waveform
a)
Crest
b)
Wavelength
c)
Frequency
d)
Period
16.
Lines of flux generated by one winding which do not link the other winding
a)
Flux loss
b)
Leakage flux
c)
Reactance leakage
d)
Inductance leakage
17.
What determines whether a substance is an insulator or a conductor?
a)
Number of protons
b)
Number of Photons
c)
Number of valence electrons
d)
Number of neutrons
18.
Which of the following is positive electricity?
a)
Resinous dynamic electricity
b)
Vitreous dynamic electricity
c)
Vitreous static electricity
d)
Resinous static electricity
19.
If the magnitude of the potential difference is generated by a single conductor passing through a magnetic field, which of the following statements is FALSE?
a)
The potential difference depends on the speed with which the conductor cuts the magnetic field
b)
The potential difference depends on the length of the conductor that cuts the magnetic field
c)
The potential difference depends on the magnetic field density that is present
d)
The potential difference depends on the diameter of the conductor that cuts the magnetic field
20.
A current of 10-A flows through a 1 mm diameter wire. What is the average number of electrons that pass through a cross section of the wire per second?
a)
1.6 x 1018 e/s
b)
6.2 x 1018 e/s
c)
1.6 x 1019 e/s
d)
6.3 x 1019 e/s
21.
Which of the following statements is true for steady-state conditions in a circuit powered by a dry a cell?
a)
Voltage is dependent upon time
b)
Capacitors behave as short circuits
c)
Inductors behave as short circuits
d)
Resistors behave as open circuits
22.
What is the internal resistance of a 9 V battery that delivers 100 A when its terminals are shorted?
a)
0.09 Ω
b)
11 Ω
c)
1.0 Ω
d)
90 Ω
23.
The change in the direction of a compass needle, when a current-carrying wire is brought near, is:
a)
Electromagnetic deflection
b)
Electrostatic force
c)
Magnetic force
d)
Electroscopic force
24.
Suppose a certain current in a galvanometer causes the needle to deflect 20 degrees, and then this current is doubled. The needle deflection:
a)
Will decrease
b)
Will stay the same
c)
Will increase
d)
Will reverse direction
25.
A unidirectional form of DC can be derived from which of the following sources?
a)
Battery
b)
Generator
c)
Rectifier circuits
d)
Power supply
26.
2.4 V of DC voltage can be obtained from how many NiMH cells connected in series?
a)
2
b)
3
c)
4
d)
6
27.
A dc voltage is applied across a certain value of resistance. If the resistance value is halved, by what factor must the voltage be multiplied if the dissipated power is unchanged?
a)
0.5 W
b)
0.25 W
c)
4 W
d)
0.707 W
28.
You have an unlimited supply of 1-W, 1000-Ω resistors, and you need a 500-Ω resistance rated at 7 W or more. This can be done by assembling:
a)
Four sets of two 1000-Ω resistors in series, and connecting these four sets in parallel
b)
Four sets of two 1000-Ω resistors in parallel, and connecting these four sets in series
c)
A 3×3 series-parallel matrix of 1000-Ω resistors
d)
Something other than any of the above
29.
Where are electrons being pumped in a circuit powered by a battery?
a)
From negative terminal around to positive terminal
b)
from positive terminal around to negative terminal
c)
back and forth from the terminal to terminal
d)
all of the choices
30.
Bleeder resistors:
a)
Are connected across the capacitor in a power supply
b)
Keep a transistor from drawing too much current
c)
Prevent an amplifier from being overdriven
d)
Optimize the efficiency of an amplifier
31.
Which of the following method/laws defines a node every junction in the network that represents a connection of three or more branches?
a)
Kirchhoff’s Current Law
b)
Kirchhoff’s Voltage Law
c)
Nodal method
d)
Maxwell’s method
32.
A major feature of a pot-core winding is:
a)
High current capacity
b)
Large inductance in small volume
c)
Efficiency at very high frequencies
d)
Ease of inductance adjustment
33.
As an inductor core material, air:
a)
Has excellent efficiency
b)
Has high permeability
c)
Allows large inductance in a small volume
d)
Has permeability that can vary over a wide range
34.
How many nodes are needed to solve an electrical network using nodal method?
a)
All the nodes in the circuit
b)
All nodes less one node
c)
Five nodes
d)
All nodes less two nodes
35.
The power loss in an iron-core transformer or other AC devices as a result of magnetic hysteresis
a)
Inductive loss
b)
Hysteresis loss
c)
Magnetic loss
d)
Magnetic power loss
36.
What is the inferred absolute zero temperature of silver?
a)
-243°C
b)
-236°C
c)
-234.5°C
d)
-242°C
37.
Which of the following materials increase very slightly in resistance with a rise in temperature?
a)
Conductor
b)
Insulator
c)
Dielectric
d)
Alloy
38.
What static electricity can be produced by rubbing silk on a glass rod?
a)
Resinous electricity
b)
Vitreous electricity
c)
Positive static electricity
d)
Negative static electricity
39.
Determine how long a battery will last whose rating is 100 Ah, 24 V and will run a 300-W electronic equipment and 50-W light.
a)
26.65 hours
b)
50.05 hours
c)
6.85 hours
d)
12.00 hours
40.
The resistance of 575 m of a certain wire of 21.85Ω. How much must be cut off to reduce the resistance to 14.25 Ω?
a)
375 m
b)
575 m
c)
20 m
d)
200 m
41.
If the fifth color in a carbon composition resistor coding is brown, what is the failure rate (%/1000-hr)?
a)
1
b)
0.001
c)
0.1
d)
0.01
42.
Two 0.1 µF capacitors are connected in parallel across a 120-Vdc source. The voltage source is then removed and a third unchanged 0.1 µF capacitor is connected across the parallel combination. What is the voltage across the third capacitor?
a)
80 V
b)
60 V
c)
120 V
d)
40 V
43.
A resistor of 0.0044 siemens, a capacitor whose susceptance is 0.035 Siemens, and a coil whose susceptance is -0.011 siemens are all connected in parallel. The admittance vector is:
a)
0.0044 + j0.024
b)
0.035 – j0.011
c)
-0.011 – j0.035
d)
0.0044 + j0.046
44.
Which of the following is negative electricity?
a)
Dynamic electricity
b)
Resinous static electricity
c)
Vitreous static electricity
d)
Vitreous electricity
45.
Air works well as a dielectric mainly because it:
a)
Has a high dielectric constant
b)
Is not physically dense
c)
Has low loss
d)
Allows for large capacitance in a small volume
46.
Which of the following types of capacitors is polarized?
a)
Paper
b)
Mica
c)
Interelectrode
d)
Electrolytic
47.
A copper wire has a resistance of 5 Ω. What is the resistance of another copper wire at the same temperature with length twice as long but with one half the diameter?
a)
25 Ω
b)
15 Ω
c)
40 Ω
d)
20 Ω
48.
To get the Thevenin voltage, you have to
a)
short the voltage source
b)
short the load resistor
c)
open the load resistor
d)
open the voltage source
49.
If a capacitor has a negative temperature coefficient:
a)
Its value decreases as the temperature rises
b)
Its value increases as the temperature rises
c)
Its value does not change with temperature
d)
It must be connected with the correct polarity
50.
A conductor of unknown length has a diameter of 250 mils and a resistance of 280 Ω. By several successive passes through drawing dies, the diameter is reduced to 50 mils. Assuming that the resistivity of the conductor remains unchanged in the drawing process, what is the resistance of the reduced size wire?
a)
175 Ω
b)
250 Ω
c)
560 Ω
d)
150 Ω
51.
Mercuric oxide is a primary cell with a nominal open circuit voltage of
a)
1.35 V
b)
2.1 V
c)
1.25 V
d)
1.5 V
52.
What resistor is commonly used in power circuits?
a)
Carbon composition resistor
b)
Thin-film resistor
c)
Wire-wound resistor
d)
Potentiometer
53.
A coil of 3.50 µH and a capacitor of 47.0 pF are in parallel. The frequency is 9.55 MHz. There is nothing else in series or parallel with these components. What is the admittance vector?
a)
0 + j0.00282
b)
0 – j0.00194
c)
0 + j0.00194
d)
0 – j0.00758
54.
Which of the following is not a characteristic of mica capacitors?
a)
High efficiency
b)
Small size
c)
Capability to handle high voltages
d)
Low loss
55.
A vector pointing “southeast” in the GB plane would indicate the following:
a)
Pure conductance, zero susceptance
b)
Conductance and inductive susceptance
c)
Conductance and capacitive susceptance
d)
Pure susceptance, zero conductance
56.
Which tolerance color is GMV?
a)
Red
b)
Silver
c)
Gold
d)
Yellow
57.
What voltage can be applied across a capacitor for a very short period of time?
a)
Transient voltage
b)
working voltage
c)
Surge voltage
d)
Plate voltage
58.
When an alternating voltage reverse in polarity, the current it produces
a)
reverse in direction
b)
has a steady DC value
c)
has a phase angle of 180°
d)
alternate at 1.4 times the frequency of the applied voltage
59.
The inductance of a coil can be continuously varied by:
a)
Varying the frequency
b)
Varying the net core permeability
c)
Varying the current in the coil
d)
Varying the wavelength
60.
A copper-wire conductor with 0.2 in diameter has an area of
a)
200 cmil
b)
20, 000 cmil
c)
40, 000 cmil
d)
400 cmil
61.
The hot resistance of the tungsten in a bulb is higher than its cold resistance because the filament’s temperature coefficients is
a)
negative
b)
positive
c)
zero
d)
about 10 Ω per degree
62.
Which of the following does not increase the loss in a transmission line?
a)
Reducing the power output of the source
b)
Increasing the degree of mismatch between the line and the load
c)
Reducing the diameter of the line conductors
d)
Raising the frequency
63.
Power factor is defined as the ratio of:
a)
True power to VA power
b)
True power to imaginary power
c)
Imaginary power to VA power
d)
Imaginary power to true power
64.
Which of the following is the temperature coefficient of resistance of silver?
a)
0.00393
b)
0.0039
c)
0.00382
d)
0.0038
65.
In the sign convention of Kirchhoff’s laws, if we traverse in the direction of current in a resistance, it is
a)
voltage rise
b)
voltage drop
c)
positive
d)
negative
66.
The shell method of transformer winding:
a)
Provides maximum coupling
b)
Minimizes capacitance between windings
c)
Withstands more voltage than other winding methods
d)
Has windings far apart but along a common axis
67.
A type of resistor with typical resistance values range from 2.7 Ω to 22 MΩ
a)
Wire-wound resistor
b)
Carbon composition
c)
Thin-film resistor
d)
Potentiometer
68.
What is the dielectric strength of air dielectric?
a)
150 V/mil
b)
75 V/mil
c)
75 V/in
d)
150 V/in
69.
What is current in a chemical cell?
a)
It is a movement of positive hole charges
b)
It is a movement of positive and negative ions
c)
It is a movement of positive ions only
d)
It is a movement of negative ions only
70.
To get the Norton current, you have to
a)
short the load resistor
b)
open the voltage source
c)
open the load resistor
d)
short the voltage source
71.
Which of the following is the strongest dielectric material?
a)
Glass
b)
Paper
c)
Teflon
d)
Rubber
72.
A 2 MΩ resistor and a 2 µF capacitor are connected in series across a 100-V source. How much time is required for the voltage across the capacitor to be 63 V?
a)
1 s
b)
2 s
c)
3 s
d)
4 s
73.
Which of these core types, in general, is best if you need a winding inductance of 1.5 H?
a)
Air core
b)
Ferromagnetic solenoid core
c)
Ferromagnetic toroid core
d)
Ferromagnetic pot core
74.
An advantage of a toroid core over a solenoid core is:
a)
The toroid works at higher frequencies
b)
The toroid confines the magnetic flux
c)
The toroid can work for dc as well as for ac
d)
It’s easier to wind the turns on a toroid
75.
Which solution to network problems involves a set of independent loop currents assigned to as many as meshes as there are in a circuit?
a)
KCL
b)
KVL
c)
Nodal method
d)
Maxwell’s method
76.
In the body-end-dot method of coding for composition/wire-wound/thin-film resistor, the dot represents
a)
First significant digit
b)
Second significant digit
c)
Multiplier
d)
tolerance
77.
At five time constants, the transient current is how much percent of its steady state value?
a)
98.2%
b)
86.8%
c)
99.3%
d)
95%
78.
A method of solution applicable only to linear and bilateral networks
a)
Kirchhoff’s laws
b)
Nodal method
c)
Maxwell’s method
d)
Superposition theorem
79.
High voltage is used in long-distance power transmission because:
a)
It is easier to regulate than low voltage
b)
The I2R losses are lower
c)
The electromagnetic fields are stronger
d)
Smaller transformers can be used
80.
In a household circuit, the 234-V power has:
a)
One phase
b)
Two phases
c)
Three phases
d)
Four phases
81.
What is the unit of electric field strength or intensity?
a)
N/C
b)
N/m
c)
V/m
d)
Both A and C
82.
The zero-degree phase point in an ac sine wave is usually considered to be the instant at which the amplitude is:
a)
Zero and negative-going
b)
At its negative peak
c)
Zero and positive-going
d)
At its positive peak
83.
What is the susceptance (in Siemens) of a circuit if the impedance is 1 – j2 Ω?
a)
2
b)
0.1
c)
0.2
d)
0.4
84.
A coil has a reactance of 4.00 Ω. What is the admittance vector, G + jB, assuming nothing else is in the circuit?
a)
0 + j0.25
b)
0 + j4.00
c)
0 – j0.25
85.
If an alternating voltage is given by V = 30 sin 314t, what is the time required by the voltage to reach its negative peak for the first time?
a)
0.03 s
b)
0.02 s
c)
0.015 s
d)
0.1 s
86.
The impedance of an RC circuit is 100 Ω. If the circuit current leads the applied by the voltage by 45˚, then what is the capacitive reactance?
a)
70.7 Ω
b)
100 Ω
c)
141.42 Ω
d)
50 Ω
87.
What will happen to the susceptance of a capacitor if the frequency is doubled, all other things being equal?
a)
It will decrease to half its former value
b)
It will not change
c)
It will double
d)
It will quadruple
88.
A 200 V, 50 Hz inductive circuit takes a current of 10 A, lagging 30˚. The inductive reactance of the circuit is
a)
20 Ω
b)
10 Ω
c)
17.32 Ω
d)
16 Ω
89.
What is the power factor of an AC circuit with 6 Ω resistance and 12 Ω inductive reactance?
a)
0.8 lagging
b)
0.5 lagging
c)
0.8 leading
d)
0.5 leading
90.
A capacitor of 1 µF capacitance is charged to 100 V and then disconnected from the power supply. A second but uncharged capacitor of 3 µF is then connected across the first capacitor. The voltage across the parallel combination is
a)
25 V
b)
66 2/3 V
c)
110 V
d)
45 V
91.
Two coils of inductance is 3 H, calculate the equivalent inductance of the combination if mutual inductance assists and if mutual inductance opposes the self-inductance respectively.
a)
2.4 H and 1.4 H
b)
6.25 H and 2.75 H
c)
3.75 H and 0.94 H
d)
16 H and 4H
92.
How is electrical energy wasted in a circuit?
a)
Converted to vibration
b)
Dissipated as light
c)
Dissipated as heat
d)
Converted to radio waves
93.
What is the rapidity with which the electrical current changes direction?
a)
period of alternating current
b)
Wavelength of alternating current
c)
frequency of alternating current
d)
ohms
94.
What color bands will a resistor of 10 Ω ± 5% tolerance have
a)
Brown, Black, Black, Gold
b)
Brown, Black, Brown, Gold
c)
Brown, Brown, Black, Gold
d)
Brown, Brown, Brown, Gold
95.
A current of 0.50 A flows in an electromagnet of negligible resistance when it is connected to a source of 120-V, 60 Hz alternating current. The inductance of the electromagnet is
a)
0.01 mH
b)
0.64 H
c)
0.16 H
d)
0.24 H
96.
In a sine-wave AC circuit with XL and R in series, the
a)
voltages across R and XL are in phase
b)
voltages across R and XL are 180° out of phase
c)
voltage across R lags the voltage across XL by 90°
d)
voltage across R leads the voltage across XL by 90°
97.
Which of the theorems below is valid only in passive networks?
a)
Maximum power transfer theorem
b)
Compensation theorem
c)
Reciprocity theorem
d)
Millman’s theorem
98.
Given a power supply with a no load voltage of 12 volts and full load voltage of 10 volts, what is the percentage of voltage regulation?
a)
17%
b)
80%
c)
20%
d)
83%
99.
After two time constant, the capacitor in an RC circuit is changed to what percentage of the supply voltage?
a)
36.8%
b)
63.2%
c)
36.55%
d)
95%
100.
The power factor of a certain circuit in which the voltage lags behind the current is 80%. To increase the power factor to 100%, it is necessary to add to the circuit additional
a)
resistance
b)
inductance
c)
capacitance
d)
impedance
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