Quiz: Electrical Engineering 07 Jan 2021

Quiz: Electrical Engineering
Exam: SSC-JE
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute

Q1. Which of the following components is not a part of hydro-electric plant?
(a)Penstock
(b)Spillway
(c)Surge tank
(d)Economiser

Q2. Which of the following is not a part of stream power plant?
(a)Switch yard
(b)Ash precipitators
(c)Draught fan
(d)Surge chamber

Q3. In an electric line, switch is connected to which of the following wire?
(a)Earth
(b)Phase
(c)Neutral
(d)Not connected

Q4. According to the IS code, the colour of earth wire is usually
(a)Red
(b)Green
(c)Yellow
(d)Black

Q5. If the maximum current of a half-wave rectified wave is 10 A, its RMS value is given by
(a)3.10 A
(b)5.0 A
(c)6.37 A
(d)7.07 A

Q6. A 3 H inductor has 2000 turns. How many turns must be added to increase the inductance to 5 H?
(a)1000 turns
(b)2500 turns
(c)2582 turns
(d)582 turns

Q7. For an R-L-C series circuit in resonance, which of the following statement is NOT CORRECT.
(a) The current is maximum at Resonance in series R-L-C circuit.
(b) The Power factor at the resonance is unity.
(c)Current is minimum at Resonance in series R-L-C circuit.
(d) Circuit Impedance at resonance = Circuit Resistance

Q8. By using guard ring in a transmission line, its string efficiency will be
(a)increase
(b)decrease
(c)constant
(d)none of the above

Q9. Which of the following starter is sufficient to start the DC series motor?
(a)4-point starter
(b)3-point starter
(c)2-point starter
(d)All of the above

Q10. Which following is a two terminal three-layer device?
(a)BJT
(b)MOSFET
(c)Power diode
(d)All of the above

SOLUTIONS
S1. Ans.(d)
Sol. The major components of a hydroelectric plant are as follows.
Forebay
Intake structure
Penstock
Surge chamber
Hydraulic turbines
Power house
Draft tube
Tailrace
Spillway is used to discharge excess water from dam.
An economiser is a mechanical device which is used as a heat exchanger by preheating a fluid to reduce energy consumption. i.e., it is used to heat feed water. It is a part of thermal power plant.

S2. Ans.(d)
Sol. Surge chamber is a part of hydro-electric power plant. Surge tank is a water storage device used as pressure neutralizer in hydropower water conveyance system to resists excess pressure rise and pressure drop conditions.

S3. Ans.(b)
Sol. If the switch were in the neutral line, the appliance would still get electricity when the switch is turned off. By switching the live wire, we make sure that no electricity flows in the appliance when it is switched off. Otherwise, we may get a shock while working on it with the switch off.

S4. Ans.(b)
Sol. According to the IS code, the colour of earth wire is usually Green.

S5. Ans.(b)
Sol. For Half-wave rectifier: i_rms=i_m/2=10/2=5 A

S6. Ans.(d)
Sol. As we know, L α N^2
∴(N_2^2)/(N_1^2 )=L_2/L_1
∴N_2=N_1×√(L_2/L_1 )=2000×√(5/3)=2582
Added number of turns=2582-2000=582.

S7. Ans.(c)
Sol. In a series RLC circuit, at resonance the voltage drops across the capacitance and
inductance is equal in magnitude. But in Phase Opposition so the impedance will be
minimum at resonance hence the current at the resonance is maximum. & the Power Factor at Resonance is Unity.

S8. Ans.(a)
Sol. Guard ring serves following purposes:
A. Equalization of voltage drop across the units
B. Protect the insulator strings from the flashover whenever over-voltage occurs between
the tower structure and the power conductor.
C. Due to this string efficiency increases.

S9. Ans.(c)
Sol. 2-point starter is enough to start the dc series motor. Since armature and field winding are in series. No requirement of 3- or 4-point starter.

S10. Ans.(c)
Sol. The power diodes are similar to p-n junction or low power diodes but have large power, voltage and current handling capabilities than those of conventional p-n junction diodes. It has two terminal and three layers. It finds many applications in electronics and electrical engineering circuits.

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