NHPC-JE’21 EE: Daily Practices Quiz 27-Oct-2021

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NHPC-JE’21 EE: Daily Practices Quiz

NHPC-JE’21 EE: Daily Practices Quiz 27-Oct-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. Which of the following causes permanent damage to a transmission line insulator?
(a) Corona discharge
(b) Puncture
(c) Dry band arcing
(d) Flashover

Q2. Which of following relay is used for transformer protection?
(a) Mho relay
(b) Distance relay
(c) Impedance relay
(d) Buchholz relay

Q3. An amplifier has a voltage gain 60 and β = 100. The power gain of the amplifier is:
(a) 6000
(b) 600
(c) 1.66
(d) 0.6

Q4. Which of the following yields high starting torque?
(a) DC shunt motor
(b) DC series motor
(c) Differential-compound motors
(d) Cumulative-compound motors

Q5. An amplifier has a voltage gain A_v=1000. The voltage gain in dB is:
(a) 3 dB
(b) 20 dB
(c) 30 dB
(d) 60 dB

Q6. Which gates are known as universal gates?
(a) NAND & NOR
(b) AND & NOT
(c) OR & NOT
(d) AND & OR

SOLUTIONS

S1. Ans.(b)
Sol. As puncture destroys the insulator, it is more serious than flash-over. Therefore, Safety Factor is defined for an Insulator. Safety factor of an Insulator is defined as the ration of Puncture Voltage to the Flash Over Voltage.
Safety Factor = Puncture Voltage / Flash Over Voltage
So, (Puncture Voltage)/ (Flash Over Voltage)>1.

S2. Ans.(d)
Sol. Buchholz relay.

S3. Ans.(a)
Sol. Power gain=β×voltage gain=100×60=6000.
Note: voltage gain=β×(R_out/R_in )

S4. Ans.(b)
Sol. DC series motor.

S5. Ans.(d)
Sol. Voltage gain in dB=20 log⁡〖A_V=20 log⁡〖1000=20 log⁡〖10^3=3×20=60 dB.〗 〗 〗

S6. Ans.(a)
Sol. NAND & NOR gates are universal gates.

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