問題一覧
1
When installing two grounding electrodes, the minimum distance between them is
1,800 mm
2
The current flowing in L and C at parallel resonance are
equal
3
What does PEMC in EPIRA stands for?
Philippine Electricity Market Corporation
4
For two alternators operating in parallel, if the load shared by one of them is to be increased, its field
excitation is
to be kept constant but input torque should be increased
5
open circuit test on transformers is conducted to determine
core loss
6
Which of the following power plant is a conventional squrce of energy?
Coal energy
7
In a synchronous motor, the magnitude of stator back emf depends on
dc excitation only
8
PDC in EPIRA MEANS
Philippine Distribution Code
9
What is the maximum plug and cord rating of a 30-A branch circuit?
24 A
10
Alternators installed in a hydro power station, are of
medium speed
11
A sine wave has a frequency of 60 Hz. Its angular frequency is
120
12
In a loss-free RLC circuit, the transient current is
Sinusoidal
13
At very low frequencies a series RC circuit behaves as almost purely
capacitive
14
One of the advantages of distributing the winding in alternators is to
improve voltage waveform
15
The effect of corona is
increased energy loss
16
The mms value of pure cosine function is
0.707 of peak value
17
What is the equivalent IEEE device function number for directional power relay?
32
18
Energy radiated continuously in the form of lighting waves is called
Luminous flux
19
Efficiency is secondary consideration in case of
peak load plants
20
The condition of a liquid electrolyte is measured in terms of its
specific gravity
21
If the field of a dc shunt motor is opened
the speed of the motor will become very high
22
ideal full.-wave rectifier with non-inductive load has zero transformation losses. What is the efficiency?
80%
23
The dummy coil in dc machines is used to
bring about mechanical balance of armature
24
The purpose of insulating oil when used on power circuit breaker are the following, EXCEPT:
Interrupter
25
Inside a hollow spherical conductor
electric field is zero
26
Residual magnetism is necessary in a
Self excited generator
27
In case of delta connected circuit, when one resistor is open, power will be
reduced by 1/3
28
With reference to armature windings, wave windings are often called __________ windings
series
29
This is the compact arrangement of switching devices:
Switchgear
30
Which of the following is NOT INCLUDED in the Technical Performance Standards for Distribution and
Supply set by the Philippine Distribution Code?
Collection efficiency
31
Three 3-ohm resistors are connected in parallel. This combination is then placed in series with another 3-
ohm resistor. What is the equivalent resistance in ohm?
4
32
Which plant takes the least time in starting from cold Coes to full load operation?
Gas turbine power plant
33
What is the equivalent IEEE device number for an under-voltage relay?
27
34
To adjust the power of the ajternator, adjust the
governor
35
In a transmission line of negligible resistance, the surge impedance will be
square root of L/C
36
What is the purpose of reactor in short circuit?
To lessen the current in short circuit
37
For constant transmission efficiency, voltage is increased n times, the size of the conductor would be
reduced to (1/n²) times of the original
38
Copper loss of a transformer are determined by means of a/an
short circuit
39
The power transmission capacity of the transmission is
proportional to the square of the voltage
40
The undervoltage relays are usually used for what protection of the electrical equipment?
motor protection
41
Which of the following type of fault used only the equivalent positive sequence impedance of the circuit in
the short-circuit calculation?
Three phase fault
42
What device is used to measure the temperature of a motor winding while the motor is in operation
Resistance temperature detector
43
Which of the following is a primary disadvantage of FM over AM?
Excessive use of spectrum space
44
Which of the following that the voltage regulation is one of the important factors consider in the electrical
power design?
feeder
45
Which of these is not a factor in the selection of fuse rating for protection of a branch circuit?
System impedance
46
Which of the following principle will the operation of fiber-optic cable is based?
reflection
47
When the voltage remains the same, the current will _________ as the impedance decreases.
I. decrease ll. increase
II only
48
When electrons build up pressure at one point, it is called
current flow
49
Which of the following type of fault used only the equivalent positive and negative sequence impedance of
the circuit in the short-circuit calculation?
Line to line
50
Based on the Philippine Distribution Code, all users of the distribution system must maintain a certain
power factor at the connection point in order to maintain power quality in the system. What power factor
should be maintained at the connection point?
Not less than 85%
51
Which of the following is NOT considered in the selection of surge arrester?
Insulation level
52
A 4-pole de machine is wound duplex lap. Find the number of parallel paths.
8
53
The specific gravity of a lead-acid cell is often used as a measure of its
state of charge
54
The purpose of insulating gj! when used on power circuit breaker are the following, EXCEPT;
Interrupter
55
The commonly used light sensor in a modern fax machine is the
charge couple device
56
A standard candle emits a total luminous flux of_______ lumens.
12.57
57
A space station with communication equipment that synchronizes with the earth's orbit.
Satellite
58
Impurities in an electrolyte can cause an internal short circuit condition called
Local action
59
As load power factor of an alternator becomes more lagging, the value of generated voltage required to
ive rated terminal voltage
Increases
60
In a commutator
mica is harder than copper
61
The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day d night is taken care of by which part of transformer?
Conservator
62
The material commonly used for insulation in high voltage cables is
paper
63
A frequency of 27 MHz has a wavelength of approximately
11 m
64
For a series RLC circuit at resonance, the current amplitude is __________ for a fixed voltage amplitude and the power factor is _______
maximum, unity
65
If the length of a cable is doubled, its capacitance
Becomes double
66
A central station has annual factors as follows:
Load = 58.5% Capacity = 40.9% Use = 45.2%
The reserve carried over and above the peak load is 8,900 kW. What is the installed capacity?
29,600 KW
67
Wye-delta starting is equivalent to autotransformer stacting with ________ tapping.
58%
68
These days DC motors are widely used in
electric tractions
69
Breather mounted on transformer tank contains
calcium
70
As load power factor of an alternator becomes more leading, the value of generated voltage required to
give rated terminal voltage.
decreases
71
The process by which metallic parts are demagnetized is called
degaussing
72
Synchronous motors are
notself starting
73
It is difficult to magnetize steel because of its
low permeability
74
Present day capacitors which have high capacitance in small size use a dielectric of
ceramic
75
The current-carrying capacity of a copper wire having twice the diameter of another copper wire is _______ as great
four times
76
The output current corresponding to maximum efficiency for a transformer having core loss of 100 watts
and equivalent resistance referred to secondary of 0.25 0 is amperes.
20
77
What kind of device is a diode?
Nonlinear
78
In a shunt generator the voltage builds up till constrained by
Saturation of iron
79
Slip rings are made of
copper
80
For proper parallel operation, ac polyphase alternators must have the same
voltage rating
81
A transmitter supplies 10 KW of carrier power to the antenna. The total radiated power with 40% modulation is ___________ KW.
10.8
82
The series field of a short-shunt compound dc generator is excited by
load
83
The reciprocal of permeability
reluctivity
84
For which of the following sinusoids, the rms value and mean value is the same?
square wave
85
The maximum efficiency of a half-wave rectifier is
40.6%
86
Ideal transformer assumptions do not include
zero reactance of the winding
87
Aswitch is connected across a 220 v supply. What is the voltage across the switch if it is opened?
220 v
88
If the load current and flux of a dc motor are held constant and voltage applied across its armature is
increased by 10 percent, its speed will
increase by about 10%
89
If there is an open circuit in the rotor of SCIM
motor will not start
90
In a synchronous machine when the rotor speed becomes more than the synchronous speed during hunting, the damping bars develop ________ torque.
induction generator
91
At leading p.f., the armature flux in an alternator the rotor flux.
aids
92
This is the rating of power circuit breakers used to be the basis in replacing its contacts
duty cycle
93
An amplifier has an output of 50 watts. What is its output in dBm
47
94
The voltage applied across the resistor was reduced by 50%. The power consumed by the resistor will be reduced by
_____%
75
95
The effect of the dielectric is to
reduce the working voltage
96
One KWHR is equal to ______ BTU
3413
97
Heating effect of current has an undesirable side effect in
vacuum cleaner
98
When the sole purpose of an alternating current is to produce heat, the selection of conductor is based
on ________ value of the current
root mean square
99
What is the primary advantage of FM over AM?
noise immunity
100
Which of the following is not included in the evaluation of the Technical Performance of a Distribution
System according to Philippine Distribution Code (PDC)?
collecting efficiency
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100問 • 1年前問題一覧
1
When installing two grounding electrodes, the minimum distance between them is
1,800 mm
2
The current flowing in L and C at parallel resonance are
equal
3
What does PEMC in EPIRA stands for?
Philippine Electricity Market Corporation
4
For two alternators operating in parallel, if the load shared by one of them is to be increased, its field
excitation is
to be kept constant but input torque should be increased
5
open circuit test on transformers is conducted to determine
core loss
6
Which of the following power plant is a conventional squrce of energy?
Coal energy
7
In a synchronous motor, the magnitude of stator back emf depends on
dc excitation only
8
PDC in EPIRA MEANS
Philippine Distribution Code
9
What is the maximum plug and cord rating of a 30-A branch circuit?
24 A
10
Alternators installed in a hydro power station, are of
medium speed
11
A sine wave has a frequency of 60 Hz. Its angular frequency is
120
12
In a loss-free RLC circuit, the transient current is
Sinusoidal
13
At very low frequencies a series RC circuit behaves as almost purely
capacitive
14
One of the advantages of distributing the winding in alternators is to
improve voltage waveform
15
The effect of corona is
increased energy loss
16
The mms value of pure cosine function is
0.707 of peak value
17
What is the equivalent IEEE device function number for directional power relay?
32
18
Energy radiated continuously in the form of lighting waves is called
Luminous flux
19
Efficiency is secondary consideration in case of
peak load plants
20
The condition of a liquid electrolyte is measured in terms of its
specific gravity
21
If the field of a dc shunt motor is opened
the speed of the motor will become very high
22
ideal full.-wave rectifier with non-inductive load has zero transformation losses. What is the efficiency?
80%
23
The dummy coil in dc machines is used to
bring about mechanical balance of armature
24
The purpose of insulating oil when used on power circuit breaker are the following, EXCEPT:
Interrupter
25
Inside a hollow spherical conductor
electric field is zero
26
Residual magnetism is necessary in a
Self excited generator
27
In case of delta connected circuit, when one resistor is open, power will be
reduced by 1/3
28
With reference to armature windings, wave windings are often called __________ windings
series
29
This is the compact arrangement of switching devices:
Switchgear
30
Which of the following is NOT INCLUDED in the Technical Performance Standards for Distribution and
Supply set by the Philippine Distribution Code?
Collection efficiency
31
Three 3-ohm resistors are connected in parallel. This combination is then placed in series with another 3-
ohm resistor. What is the equivalent resistance in ohm?
4
32
Which plant takes the least time in starting from cold Coes to full load operation?
Gas turbine power plant
33
What is the equivalent IEEE device number for an under-voltage relay?
27
34
To adjust the power of the ajternator, adjust the
governor
35
In a transmission line of negligible resistance, the surge impedance will be
square root of L/C
36
What is the purpose of reactor in short circuit?
To lessen the current in short circuit
37
For constant transmission efficiency, voltage is increased n times, the size of the conductor would be
reduced to (1/n²) times of the original
38
Copper loss of a transformer are determined by means of a/an
short circuit
39
The power transmission capacity of the transmission is
proportional to the square of the voltage
40
The undervoltage relays are usually used for what protection of the electrical equipment?
motor protection
41
Which of the following type of fault used only the equivalent positive sequence impedance of the circuit in
the short-circuit calculation?
Three phase fault
42
What device is used to measure the temperature of a motor winding while the motor is in operation
Resistance temperature detector
43
Which of the following is a primary disadvantage of FM over AM?
Excessive use of spectrum space
44
Which of the following that the voltage regulation is one of the important factors consider in the electrical
power design?
feeder
45
Which of these is not a factor in the selection of fuse rating for protection of a branch circuit?
System impedance
46
Which of the following principle will the operation of fiber-optic cable is based?
reflection
47
When the voltage remains the same, the current will _________ as the impedance decreases.
I. decrease ll. increase
II only
48
When electrons build up pressure at one point, it is called
current flow
49
Which of the following type of fault used only the equivalent positive and negative sequence impedance of
the circuit in the short-circuit calculation?
Line to line
50
Based on the Philippine Distribution Code, all users of the distribution system must maintain a certain
power factor at the connection point in order to maintain power quality in the system. What power factor
should be maintained at the connection point?
Not less than 85%
51
Which of the following is NOT considered in the selection of surge arrester?
Insulation level
52
A 4-pole de machine is wound duplex lap. Find the number of parallel paths.
8
53
The specific gravity of a lead-acid cell is often used as a measure of its
state of charge
54
The purpose of insulating gj! when used on power circuit breaker are the following, EXCEPT;
Interrupter
55
The commonly used light sensor in a modern fax machine is the
charge couple device
56
A standard candle emits a total luminous flux of_______ lumens.
12.57
57
A space station with communication equipment that synchronizes with the earth's orbit.
Satellite
58
Impurities in an electrolyte can cause an internal short circuit condition called
Local action
59
As load power factor of an alternator becomes more lagging, the value of generated voltage required to
ive rated terminal voltage
Increases
60
In a commutator
mica is harder than copper
61
The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day d night is taken care of by which part of transformer?
Conservator
62
The material commonly used for insulation in high voltage cables is
paper
63
A frequency of 27 MHz has a wavelength of approximately
11 m
64
For a series RLC circuit at resonance, the current amplitude is __________ for a fixed voltage amplitude and the power factor is _______
maximum, unity
65
If the length of a cable is doubled, its capacitance
Becomes double
66
A central station has annual factors as follows:
Load = 58.5% Capacity = 40.9% Use = 45.2%
The reserve carried over and above the peak load is 8,900 kW. What is the installed capacity?
29,600 KW
67
Wye-delta starting is equivalent to autotransformer stacting with ________ tapping.
58%
68
These days DC motors are widely used in
electric tractions
69
Breather mounted on transformer tank contains
calcium
70
As load power factor of an alternator becomes more leading, the value of generated voltage required to
give rated terminal voltage.
decreases
71
The process by which metallic parts are demagnetized is called
degaussing
72
Synchronous motors are
notself starting
73
It is difficult to magnetize steel because of its
low permeability
74
Present day capacitors which have high capacitance in small size use a dielectric of
ceramic
75
The current-carrying capacity of a copper wire having twice the diameter of another copper wire is _______ as great
four times
76
The output current corresponding to maximum efficiency for a transformer having core loss of 100 watts
and equivalent resistance referred to secondary of 0.25 0 is amperes.
20
77
What kind of device is a diode?
Nonlinear
78
In a shunt generator the voltage builds up till constrained by
Saturation of iron
79
Slip rings are made of
copper
80
For proper parallel operation, ac polyphase alternators must have the same
voltage rating
81
A transmitter supplies 10 KW of carrier power to the antenna. The total radiated power with 40% modulation is ___________ KW.
10.8
82
The series field of a short-shunt compound dc generator is excited by
load
83
The reciprocal of permeability
reluctivity
84
For which of the following sinusoids, the rms value and mean value is the same?
square wave
85
The maximum efficiency of a half-wave rectifier is
40.6%
86
Ideal transformer assumptions do not include
zero reactance of the winding
87
Aswitch is connected across a 220 v supply. What is the voltage across the switch if it is opened?
220 v
88
If the load current and flux of a dc motor are held constant and voltage applied across its armature is
increased by 10 percent, its speed will
increase by about 10%
89
If there is an open circuit in the rotor of SCIM
motor will not start
90
In a synchronous machine when the rotor speed becomes more than the synchronous speed during hunting, the damping bars develop ________ torque.
induction generator
91
At leading p.f., the armature flux in an alternator the rotor flux.
aids
92
This is the rating of power circuit breakers used to be the basis in replacing its contacts
duty cycle
93
An amplifier has an output of 50 watts. What is its output in dBm
47
94
The voltage applied across the resistor was reduced by 50%. The power consumed by the resistor will be reduced by
_____%
75
95
The effect of the dielectric is to
reduce the working voltage
96
One KWHR is equal to ______ BTU
3413
97
Heating effect of current has an undesirable side effect in
vacuum cleaner
98
When the sole purpose of an alternating current is to produce heat, the selection of conductor is based
on ________ value of the current
root mean square
99
What is the primary advantage of FM over AM?
noise immunity
100
Which of the following is not included in the evaluation of the Technical Performance of a Distribution
System according to Philippine Distribution Code (PDC)?
collecting efficiency