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WorksheetsEE 3-1
Total questions: 50
Worksheet time: 25mins
The voltage applied across an electric press was reduced by 50%. The power consumed by the press will be reduced to
25%
50%
60%
75%
The law that induces emf and current always opposes the cause producing them was discovered by
Faraday
Maxwell
Lenz
Ohm
Series capacitors are used to
improve the line voltage
compensate for line inductive reactance
compensate for line capacitive reactance
none of these
A 4,400 V, 60 Hz transformer has core loss of 840 watts, of which one-third is eddy current loss. What is the core loss when the transformer is connected to a 4,600 V, 60 Hz source?
926 W
907 W
873 W
944 W
Surge impedance of a transmission line is given by
√L/C
√CL
1/√LC
√C/L
Which of the following distribution systems gives greater reliability?
radial system
ring system
DC three-wire system
open-loop system
The nameplate speed of a 60 Hz, 3-phase induction motor is 1,175 rpm. What is its number of poles?
2
4
6
8
The transformer oil used in transformers provides
cooling and lubrication
insulation and lubrication
insulation and cooling
insulation, cooling, and lubrication
Two identical coupled coils have an equivalent inductance of 80 mH when connected in series aiding and 35 mH in series opposing. Find the coefficient of coupling.
0.39
0.43
0.5
0.64
To protect the Δ-Δ power transformer against fault, the CT will have
Δ-Δ connection
Δ-Y connection
Y-Δ connection
Y-Y connection
Three 6.66 Ω resistors are connected in wye. What is the equivalent of each delta connected resistor?
2.22 Ω
20 Ω
11.54 Ω
10 Ω
For detection of the occurrence of severe synchronizing power surges
impedance relays are best suited
reactance relays are best suited
MHO relays are best suited
split-phase relays are best suited
Two wattmeters both have readings of 5 kW when connected for the two-wattmeter method in a 480-V three-phase circuit that has a balanced Δ load. Find the Δ phase impedance.
69.1∠90° Ω
69.1∠-90° Ω
69.1∠45° Ω
69.1∠0° Ω
Which of the following cannot have a single unit of 100 MW?
Hydro power plant
Steam power plant
Diesel power plant
Nuclear power plant
If the capacitance of the transmission line is increased, the transmitted power will
remain same
increase
decrease
tend to zero at the receiving end
Which of the following tests are conducted for transformer oil?
I. dielectric
II. interfacial tension
III. color of oil
IV. neutralization number
V. power factor
I,II,III, and IV
I,II,III, and V
II,III,IV, and V
I,II,V, and VI
Peak load plants are designed to supply power at
low capital cost and low operating cost
high capital cost and low operating cost
low capital cost and high operating cost
high capital cost and high operating cost
A light source is located 2 m from a surface produces an illumination of 50 lx on that surface. Find the intensity of the light source in candela
100
50
150
200
Which is not a standard distribution voltage in the Philippines?
13.2 kV
13.8 kV
34.5 kV
69 kV
The power plant has a peak demand of 90 MW, capacity factor of 0.50, use factor of 0.80 and load factor of 0.60. Find the plant installed capacity.
105 MW
108 MW
110 MW
115 MW
A 500 MCM ACSR cable has 37 strands. Determine the diameter in mils of each strand.
120.24
110.35
118.34
116.25
Three unbalanced 3-phase currents are given as follows: Iₐ = 10∠-30° A, Iᵦ = 0 and I𝚌 = 10∠-150° A. Find I₀.
3.34∠150° A
3.34∠-150° A
3.34∠210° A
3.34∠-135° A
What was the maximum number of conductors in a raceway that does not need to be derated?
2
3
4
5
When peace and order problems exist, National Grid Corporation of the Philippines (NGCP) issues
security alert
imminent danger alert
trouble alert
red alert
Which increases the resistance of a conductor?
increase in size
increase in length
decrease in length
none of these
Red, red, orange, silver indicates a resistance of
22 Ω, ±5%
220 Ω, ±5%
2.2 kΩ, ±10%
22 kΩ, ±10%
A type of electronics communication in which only one party transmits at a time.
Full duplex
Half duplex
Bicom
Simplex
21 is the device function number for this relay.
Undervoltage relay
Overvoltage relay
Distance relay
Directional power relay
AC system has the following disadvantages over DC system.
skin effect exists
line regulation is more
charging current exists
proximity effect exists
A three-phase transformer rated for 33 kV/6.6 kV is connected Y-Δ and the protecting current transformer on the low voltage side has a ratio of 400/5. What is the ratio of the current transformer on the high voltage side?
46.19:2.89
46.19:5
60:5
80.2:89
RA 7832 concerns on
pilferage of electricity, theft of transmission materials and capping of system loss
pilferage of electricity, theft of transmission materials and rationalizing of system loss
pilferage of electrical energy
pilferage of electricity and electrical materials
Three resistors A, B, and C are connected in series to a 120-V supply. If the resistor A = 60 ohms and the voltage across resistor B = 40 V when the current is 1/2 A, what is the resistance of resistor C in ohms?
105
90
110
100
Open circuit test on transformers is conducted to determine
hysteresis loss
copper loss
core loss
eddy current loss
PDC in EPIRA means
Philippine Distribution Company
Philippine Distribution Corporation
Philippine Distribution Commission
Philippine Distribution Code
Three resistances of 4, 9, and 11 ohms are connected in series and then in parallel. Find the effective resistance for series connection.
15 Ω
13 Ω
20 Ω
24 Ω
What device is used to measure the temperature of a motor winding while the motor is in operation?
Seismic probe
Resistance temperature detector
Thermocouples
Proximity probe
A straight conductor 100 cm long and carrying a current of 40 A lies perpendicular to a magnetic field of 1.5 Wb/m². What is the mechanical power in watts required to move the conductor at a uniform speed of 5 m/s?
30 W
300 W
330 W
360 W
A 4-pole DC machine is wound duplex lap. Find the number of parallel paths.
4
6
8
10
When 3 A flows through a circuit with an input admittance of 0.4 + j0.5 S, what reactive power does the circuit consume?
11 var
-8.7 var
8.7 var
-11 var
Which of the following type of fault uses only the equivalent positive sequence impedance of the circuit in the short-circuit calculation?
Line to line
Line to ground
Double line to ground
Three-phase fault
The amount of frequency deviation from the carrier center of frequency in an FM transmitter is proportional to the
shape
amplitude
frequency
phase
Find the power factor of the impedance 5∠-25° Ω.
0.423 lagging
0.9063 leading
0.423 leading
0.9063 lagging
If the resistance in a series RC circuit is increased, the magnitude of the phase angle
increases
remains the same
decreases
changes in an indeterminate manner
Nuclear reactors generally employ
fusion
fission
both fusion and fission
none of these
Calculate the time delay for a phase angle of 45° at a frequency of 500 Hz.
2 ms
0.5 ms
1.5 ms
0.25 ms
A 20 µF capacitor is in parallel with a practical inductor represented by L = 1 mH in series with R = 7 Ω. Find the resonant frequency of the parallel circuit.
79.6 Hz
159.2 Hz
25.3 Hz
500 Hz
The potential difference between two conductors is 110 V. How much work is done in moving a 5 coulomb charge from one conductor to the other?
2,420 J
22 J
550 J
0.227 J
A 100-µF capacitor, carrying an initial charge of 500 µC, is discharged through a 50 Ω resistor. Determine the time it takes the capacitor to discharge to 184-µC charge.
5 ms
10 ms
15 ms
20 ms
Which of the following is not a factor in calculating the feeder conductor size?
ambient temperature
branch-circuit protection
voltage drop
demand factors
A 4-pole, 3-phase induction motor has a wye-connected stator winding and runs on a 220 V, 60 Hz supply. The rotor resistance and standstill leakage reactance are 0.1 and 0.9 ohm/phase, respectively. The ratio of rotor to stator turns/phase is 2/3. Calculate the torque developed in N·m when running with a slip of 4%.
40.4
38.2
44.7
49.5
