WorksheetsProfessional Electrical Engineering Quiz 2 part 2
Total questions: 46
Worksheet time: 23mins
A 6-pole lap wound dc generator has 240 armature conductors, a flux of 0.04 Wb per pole and runs at 1,500 rpm. If the armature resistance is 0.8 Ω, determine the current through each conductor.
300 A
100 A
50 A
25 A
An air-cored toroidal coil has 450 turns and a mean diameter of 300 mm and a cross-sectional area of 300 mm². Determine the self-inductance of the coil.
81 x 10⁻⁴ H
1.81 x 10⁻⁴ H
0.81 x 10⁻⁴ H
0.081 x 10⁻⁴ H
A 4-pole, three-phase 50 Hz induction motor develops a maximum torque of 20 N·m at 1,440 rpm. Obtain the torque exerted by the motor at 5% slip.
16.51 N-m
17.51 N-m
18.51 N-m
19.51 N-m
A transformer has negligible resistance and a p.u. reactance of 0.1. What is its voltage regulation on full load with a leading p.f. angle of 30°?
-10%
10%
5%
-5%
In an ac circuit, a low value of KVAR compared with KW indicates
maximum load current
low efficiency
high power factor
unity power factor
The frequency of the emf in the stator of a 4-pole induction motor is 60 Hz, and that in the rotor is 2 Hz. At what speed is the motor running?
1,720 rpm
1,740 rpm
1,760 rpm
1,780 rpm
The voltage across a 50-µF capacitor rises at a constant rate of 10 V/ms. Calculate the current through the capacitor.
50 mA
500 mA
5 mA
5 A
Branch circuit larger than ___ amperes shall only supply nonlighting outlet load.
15
20
30
50
In a 4-pole dynamo, the flux per pole is 15 mWb. Calculate the maximum emf induced in one of the armature conductors if armature is driven at 600 rpm.
0.6 V
0.3 V
0.94 V
0.47 V
How much larger is the rotor reactance of a SCIM at start-up than it is when the motor operates at 5 percent slip?
10 times
5 times
25 times
20 times
The velocity of electromagnetic waves in free space is given by
μ₀/ε₀
μ₀ε₀
1/√(μ₀ε₀)
√(ε₀/μ₀)
A 220 V, 3-phase, 4-wire abc system supplies unbalanced wye-connected resistances of 10 Ω, 15 Ω, and 20 Ω. Determine the total power of the system in watts.
3,995
3,560
3,385
3,495
Assuming a certain driving voltage causes the current to an initially discharged 1,000 µF capacitor to increase at a constant rate of 0.08 A/s, determine the voltage across the capacitor at t = 10 seconds.
600 V
1,500 V
2,000 V
3,000 V
The illumination on a surface is 100 lm/m². The reflection coefficient of the surface is 80%. What is the maximum brightness of the surface in Cd/m²?
80
125
100
64
Wye-delta starting is equivalent to autotransformer starting with ___ tapping.
33%
58%
85%
52%
With reference to armature windings, wave windings are often called ___ windings.
cascade
ring
multiple or parallel
series
Induced charge on insulators
resides on surface
moves inside
changes into electric current
moves outward
Human body is
insulator
low resistive
conductor
electrolyte
The presence of earth in case of overhead lines
increases the capacitance
decreases the capacitance
increases the inductance
decreases the inductance
A string insulator has 6 units. The voltage across the bottom-most unit is 20% of the total voltage. Its string efficiency is
20%
60%
75%
83.3%
The per unit value of a 2-ohm resistor at 100 MVA base and 10 KV base voltage is
4 pu
2 pu
0.5 pu
0.2 pu
A 75 MW power plant has an average load of 35,000 KW and a load factor of 65%. Find the reserve over peak.
23.41 MW
21.15 MW
25.38 MW
18.75 MW
Transformer breathes in when
load on it increases
load on it decreases
load remains constant
none of these
A hydroelectric generating station is supplied from a reservoir of capacity 6,000,000 m³ at a head of 170 m. Assume hydraulic efficiency of 80% and electrical efficiency of 90%. The fall in the reservoir level after a load of 15 MW has been supplied for 3 hours, if the area of the reservoir is 2.5 km², is closest to
5.39 cm
4.32 cm
5.98 cm
4.83 cm
The active length of each conductor placed in a DC generator armature is 0.4 m. The armature is rotated at a speed of 1,800 rpm in a magnetic field of average flux density 1.2 T. The diameter of the armature is 0.5 m. Find the emf induced in the conductor when it cuts the magnetic field at right angles.
5.65 V
11.31 V
45.24 V
22.62 V
The flux produced in the air gap between two electromagnetic pole faces is 6 × 10⁻² Wb. Length of air gap is 1.4 cm and cross-sectional area of the gap is 0.3 m². Find the magnetic field intensity.
153.2 × 10³ AT/m
155.2 × 10³ AT/m
157.2 × 10³ AT/m
159.2 × 10³ AT/m
What is the empirical formula to calculate the number of strands?
3n(n + 2) + 2
3n(n + 1) + 2
3n(n + 1) + 1
3n(3 + 3n) + 1
The shaft of synchronous motor is made of
mild steel
chrome steel
alnico
stainless steel
For a single line to ground fault, the zero sequence current is given by j3 pu. The current carried by the neutral during the fault is
j1 pu
j3 pu
j9 pu
j6 pu
A moving coil instrument requires 50 mA and 100 mV for full-scale deflection. What is the value of the shunt required to convert it to read up to 5 A?
0.0101 Ω
0.0202 Ω
0.0303 Ω
0.0404 Ω
The resistance of a winding wire made up of copper is 25 ohms at 30°C. What is its resistance when it operates at a temperature of 75°C? Assume temperature coefficient at 20°C equals 0.004/°C.
31.36 Ω
24.04 Ω
27.45 Ω
29.33 Ω
Bundled conductors are used in transmission lines, the effective capacitance and inductance will respectively
decrease and increase
increase and decrease
remain same and increase
decrease and remain same
A 40-m metallic conductor of cross-sectional area 1 mm² has a resistance of 12 Ω. Calculate the conductivity of the metal.
3.33 KS/m
333 MS/m
3.33 MS/m
33.3 MS/m
A car battery supplies 48 J of energy at 12 V over a certain period of time. Determine the charge moved during this period.
0.33 C
0.25 C
4 C
2 C
An inductive coil consumes 500 W of power at 10 A and 110 V and 60 Hz. Determine the inductance of the coil.
24 mH
25 mH
26 mH
27 mH
Two coupled coils have self-inductances L₁ = 50 mH and L₂ = 200 mH, and a coefficient of coupling K = 0.50. If i₁ = 5 sin 400t A, find the voltage at coil 2.
100 cos 400t
100 sin 400t
400 cos 400t
400 sin 400t
In a three-phase system, when the loads are perfectly balanced, the neutral current is
zero
one-third of maximum
two-thirds of maximum
at maximum
A parallel RLC circuit has R = 0.5 Ω, L = 10 mH and C = 2.5 mF. Determine the resonance frequency.
63.56 Hz
79.79 Hz
112.82 Hz
31.83 Hz
A double squirrel-cage induction motor has
two rotors moving in opposite direction
two parallel windings in stator
two parallel windings in rotor
two series windings in stator
A balanced delta connected load draws 10 A of line current and 3 KW at 220 V. Determine the value of resistance of each phase of the load.
38.1 Ω
80 Ω
23.5 Ω
33.3 Ω
Three sinusoidal generators and a battery are connected in series with a coil whose resistance and inductance are 8 Ω and 26.53 mH, respectively. The frequency and rms voltage of the respective generators are 20 Hz, 15 V, 60 Hz, 30 V, and 80 Hz, 50 V. The battery voltage is 6 V. Determine the circuit rms voltage.
10 V
60.51 V
101 V
68.5 V
A 12-KVA load A operating at 0.70 p.f. lagging and a 10-KVA load B operating at 0.80 p.f. lagging are connected in parallel and supplied by a 440 V, 60 Hz generator. Determine the system power factor.
0.767
0.727
0.747
0.787
Suppose that the consumption of energy in a certain country has a growth rate of 4 percent per year. In how many years will the energy consumption be tripled?
20.60
13.73
9.16
27.47
A 345 kV transmission line has a series impedance of (4 + j60) Ω and a shunt admittance of j(2 × 10⁻³) S. Using 100 MVA and the line voltage as base values, calculate the per unit shunt admittance of the line.
j2.38 pu
j3.57 pu
j4.76 pu
j5.95 pu
The purpose of providing dummy coils in a generator is
to reduce eddy current losses
to enhance flux density
to amplify voltage
to provide mechanical balance for the rotor
The conductors of a three-phase transmission line are arranged in the form of an equilateral triangle with sides of 6 m each. If the conductors are 500 mils in diameter and the line is 25 km long, what is its inductance per phase?
40 mH
17.75 mH
26.62 mH
35.5 mH
