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RVUNL’21 EE: Daily Practices Quiz 26-Aug-2021

RVUNL Recruitment 2021: The RVUNL exam date is released for a total of 1075 vacancies.
There are two parts for the RVUNL test, Part A and Part B.
Part A will have 60% weightage while Part B has 40% weightage out of the total marks in the online written exam.

RVUNL’21 EE: Daily Practices Quiz 26-Aug-2021
Each question carries 2 marks.
Negative marking: 0.5 mark
Total Questions: 06
Time: 08 min.

Q1. Gilbert is a unit of
(a) electromotive force
(b) magnetomotive force
(c) conductance
(d) permittivity
(e) None of the above

Q2. Which among the following transducer is an example of passive transducer?
(a) photovoltaic cell
(b) thermocouple
(c) piezoelectric transducer
(d) LVDT
(e) All of the above

Q3. When is the mechanical power developed by a dc motor maximum?
(E_b=back emf,V=applied voltage)
(a) Eb-V=0
(b) Eb=0
(c) Eb=V/2
(d) Eb+V=0
(e) None of the above

Q4. If, in a DC machine, the ratio of constant losses to armature resistance is 2, then at maximum efficiency, the magnitude of current flowing would be:
(a) 2 A
(b) 4 A
(c) 6.667 A
(d) 1.414 A
(e) 0.707 A

Q5. A single-phase load is supplied by a single-phase voltage source. If the current flow from load to the source is 10∠-150⁰ A and if the voltage at the load terminal is 100∠60⁰, then the
(a) Load absorbs real power and absorbs reactive power
(b) Load delivers real power and delivers reactive power
(c) Load absorbs real power and delivers reactive power
(d) Load delivers real power and absorbs reactive power
(e) None of the above

Q6. Surge impedance loading of a transmission line can be increased by:
1. Decreasing its voltage level
2. Reducing the length of the line
(a) Only 1 is correct
(b) Only 2 is correct
(c) Both 1 and 2 are correct
(d) Both 1 and 2 are incorrect
(e) None of the above

SOLUTIONS

S1. Ans.(b)
Sol. MMF=NI
S.I UNIT=Ampere-turn
CGS unit=Gilbert
1 Gb = (10/4π) A-turn= 0.7957747 A-turn

S2. Ans.(d)
Sol.
The transducer whose output is obtained in the form of voltage or current without any additional auxiliary source is known as the active transducer. E.g., thermocouple, photovoltaic cell, piezoelectric
the passive transducer takes power from the external energy source for transduction. E.g., thermistor, LVDT.

S3. Ans.(c)
Sol. In case of DC motor, to develop maximum mechanical power, E_b=V/2.

S4. Ans.(d)
Sol. For maximum efficiency, I_a^2 R_a=P_i
∴I_a=√(P_i/R_a )=√2=1.414 A

S5. Ans.(a)
Sol. Complex power supplied by load: S=VI^*=100∠60⁰×(10∠+150^0)
∴S=(-866-j500)VA=P+jQ
As supplied active and reactive power are negative. So, load absorbs both active and reactive power.

S6. Ans.(d)
Sol. Surge impedance loading: SIL=(KV)^2/Z_0 MW
Where; Z_0=√(L/C)
SIL is independent of length of line.
SIL can be increased by increasing voltage level and vice-versa.

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