WorksheetsProfessional Electrical Engineering Quiz 5 part 1
Total questions: 51
Worksheet time: 26mins
A material best suited for manufacturing of fuse wire is
Aluminum
Silver
Lead
Copper
In the Fleming’s left-hand rule, thumb always represents
voltage
current
direction of force on conductor
magnetic field
The net reactance in a series RLC circuit is
Xₗ
Xc
Xc + Xₗ
XL - Xc
Two resistors R₁ and R₂ are connected in parallel. R₁ is twice of R₂. If the current in R₁ is I, what is the current in R₂?
I
2I
4I
1/2
The ampere-hour capacity of a battery depends on
the thickness of the plates
the strength of the electrolytes
the area of the plates
the distance between the plates
A Y-Δ connected transformer has a turns ratio of 1. If the primary line current is 5 amperes, what is the secondary line current?
5 A
15 A
8.66 A
2.89 A
In a certain country, the energy consumption is expected to double in 10 years. Calculate the growth rate.
4%
3.96%
13.86%
6.93%
The condition in Ohm’s law is that
ratio V/I should be constant
current should be proportional to voltage
the temperature should remain constant
the temperature should vary
Two single-phase transformers with equal ratings and turns ratio are operated in parallel to supply a load of 300 KVA, 0.80 lagging power factor. Transformer A has a resistance of 2.5% and a reactance of 5.5%. Transformer B has a resistance of 2.0% and a reactance of 5.5%. Find the KVA load of each transformer.
147.7, 152.2
148.7, 151.5
149.7, 150.5
150.7, 149.5
If an electrical network having one or more than one voltage source is transformed into an equivalent electrical network with a single voltage source (which is a short circuit current of the previous circuit) with parallel internal resistance of the network with all current sources replaced by their internal resistance. The above illustration is called:
Thevenin’s theorem
Reciprocity theorem
Norton’s theorem
Superposition theorem
What is the power given V = 4 sin 3t and I = 4 sin 3t?
16 sin (3t)²
16 sin²(3t)
8 (1 - 6cos3t)
16 (1 - 6cos3t)
A 40μF capacitor is supplied with a voltage of v(t) = 100sin377t. Find the current equation.
1.51sin(377t - 90°)
1.51sin377t
1.51cos(377t + 90°)
1.51cos 377t
A 20 mH inductor draws a current of i(t) = 100sin100t. Find the voltage equation.
200sin100t
200cos100t
2000sin100t
2000cos100t
For a three-phase unbalanced load:
the power factor of each phase will be proportional to the load
the power factor of each phase will be the same
the power factor of at least one of the phases must be leading
the power factor of each phase may be different
Cellular phones operate in the frequency range of
EHF
VHF
UHF
SHF
A medium unshaded lamp hangs 8 m directly above the table. To what distance should it be lowered to increase the illumination to 2 times its former value?
2.34 m
5.66 m
4 m
4.64 m
The resistance of a copper wire at 30°C is 50Ω. If the temperature coefficient of copper at 0°C is 0.00427, what is the resistance at 100°C?
72.26Ω
63.24Ω
54.25Ω
58.15Ω
What is the maximum allowable voltage drop for lighting circuit?
3%
5%
2%
10%
What is the maximum allowable voltage drop for feeder?
1%
2%
3%
5%
Fiber optic operates on the principle of
Refraction
Reflection
Diffraction
Dispersion
The color is reserved for grounding equipment wire only.
white
green
yellow
grey
Overhead lines are protected from lightning by the use of
overhead ground conductors
surge arresters
either I or II
both I and II
An inductance of 20 mH is connected in parallel with a capacitance of 80μF. What is the frequency when Xₗ = Xc?
100 Hz
150 Hz
128.5 Hz
125.8 Hz
A horizontal powerline carries a current of 90 A. Compute the magnetic field at a point 1.5 m below the line.
1.2 × 10⁻⁵ T
1.2 × 10⁻⁴ T
1.2 × 10⁻³ T
1.2 × 10⁻² T
The synchroscope is an instrument used to indicate the
speed of a motor
phase relationship between the current and the voltage
phase relationship between two voltages
phase relationship between the true power and the reactive power
A three-phase transmission line of a two-conductor bundle is arranged horizontally with a spacing of 8 m between bundle centers. Each conductor is ACSR, 1,272,000 cmils Pheasant with GMR of 0.0468 ft. The spacing between conductors of the bundle is 45 cm. Find the per unit series reactance of the line if its length is 160 km and base is 100 MVA, 345 KV.
0.069 pu
0.059 pu
0.049 pu
0.039 pu
The current flowing in the armature conductors of a DC motor is
ac
dc
ac as well as dc
transients
A string insulator has 5 units. The voltage across the bottom-most unit is 30% of the total voltage. What is the string efficiency?
60%
66.67%
75%
83
A string insulator has 5 units. The voltage across the bottom-most unit is 30% of the total voltage. What is the string efficiency?
60%
66.67%
75%
83.33%
For a single line-to-ground fault, the zero-sequence current is given by |3.0 pu|. The current carried by the neutral during the fault is
1 pu
3 pu
9 pu
6 pu
Two single-phase transformers, each rated 75 KVA, are connected in V or open delta to serve a three-phase load of 120 KW at 0.80 power factor lagging. Determine the size in KVAR of the capacitor needed to prevent overloading of the transformers.
40.25
41.28
45.24
43.50
A time of 10 milliseconds is required for the current on a series RL DC circuit to reach 90% of its final steady-state value. What is the time constant in seconds for the circuit?
3.39 ms
4.34 ms
3.86 ms
4.25 ms
The armature current drawn by any DC motor is proportional to
the voltage applied to the motor
the torque required
the flux required in the motor
the speed of the motor
Fault level means
voltage at the point of fault
fault current
fault power factor
fault MVA
A bulb having a rating of 220 volts, 75 watts, is to be connected to a 110-volt source. What power will it draw if connected across a 110-volt source?
37.5 watts
9.375 watts
75 watts
18.75 watts
A capacitor is charged 0.23 watt-second of energy at a voltage of 48 volts. What is its capacitance?
180 μF
240 μF
200 μF
220 μF
A 20-HP, 110 V DC shunt motor has an efficiency of 88% and an exciting current of 4 amperes and an armature resistance of 0.04 ohm. What is the starting resistance required for full-load torque?
0.69 Ω
0.96 Ω
0.92 Ω
0.46 Ω
A coil of 50-ohm resistance and 150 mH inductance is connected in parallel with a 50-μF capacitor. What is the power factor of the circuit?
70% lagging
70% leading
80% lagging
80% leading
A 220-volt DC shunt motor runs at 500 rpm with an armature current of 50 amperes and an armature resistance of 0.1 Ω. Calculate the speed if the torque is halved?
510.8 rpm
508.6 rpm
505.8 rpm
502.8 rpm
A 150-MVA, 13.8-KV, Y-connected, 3Φ, 60-HZ alternator is operating at rated voltage and at no-load when a three-phase fault occurs at its terminals. If the subtransient reactance of the alternator is 0.2 pu, calculate the current the instant the fault occurs.
10,870 amps
6,276 amps
32,611 amps
31,380 amps
The capacitive reactance of a transmission line is 90,000 ohms per kilometer. Find the total capacitive reactance if the transmission line is 50 km long.
90,000 Ω
4.5 × 10⁶ Ω
180,000 Ω
1,800,000 Ω
A generating station supplies a peak load of 12,000 KW, 9,000 KW, and 6,000 KW. Calculate the maximum demand of the station and the energy it supplies in a year if its diversity factor and its average annual load factor is 1.2 and 0.7, respectively.
27,000 KW, 137.97 × 10⁶ KWHR
22,500 KW, 137.97 × 10⁶ KWHR
27,000 KW, 5.75 × 10⁶ KWHR
22,500 KW, 5.75 × 10⁶ KWHR
A load of 10 Ω was connected to a 12-volt battery. The current drawn was 1.18 amperes. What is the internal resistance of the battery?
0.35 Ω
0.17 Ω
0.25 Ω
0.30 Ω
In electroplating, the positive electrode is called the
cathode
anode
terminal
iontrap
The per unit value of a 2 ohm resistor at 100 MVA base and 10 KV base voltage is
4 pu
0.5 pu
0.2 pu
2 pu
Calculate the mean spherical candle power of a lamp emitting a flux of 1,500 lumens.
119.37 cd
1,500 cd
375 cd
477.46 cd
A piece of conductor 10 cm long moves across a magnetic field of 10,000 gauss at a velocity of 120 cm/sec. What voltage appears across the conductor?
0.24 V
6.0 V
0.12 V
120 V
A 220-volt, 10-HP, 60-HZ, three-phase induction motor having four poles is operating at full-load slip of 3%. What is the frequency of the rotor current at full-load?
60 HZ
18 HZ
1.8 HZ
180 HZ
A load of 10 MVA, 0.8 p.f. lagging, 22-KV is served by a transmission line which has a line resistance of 3 ohms and a line reactance of 10 ohms. Solve for the sending end voltage.
25,972 v
26,721 v
22,433 v
24,214 v
The core loss of a 5-KVA single-phase transformer with normal voltage applied to the primary is 75 watts. The maximum efficiency occurs 60% of full-load KVA. What is the full-load efficiency of the transformer at 0.80 power factor?
95.16%
93.38%
89.52%
91.36%
The reactance of a generator designated X" is given as 0.25 per unit based on the generator's nameplate rating of 18 KV, 500 MVA. The base for calculations is 20 KV, 100 MVA. Find X" on the new base.
0.0617 pu
0.0405 pu
0.0081 pu
0.0450 pu
