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UPRVUNL’21 EE: Daily Practices Quiz 31-July-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 08 min.

Q1. In power transformers, it is found that the iron or core losses practically varies very little, this is because
(a) Constant leakage flux
(b) Constant core flux
(c) Constant load current
(d) Constant leakage and core flux

Q2. Which of the conditions is must be fulfilled for a satisfactory parallel operation of transformers?
(a) Correct polarity
(b) Same pu impedance
(c) Same voltage ratio
(d) Leakage impedance should be inversely proportional to the KVA of the transformer

Q3. The qualities aspired to obtain a good permanent magnet is/are
(a) High coercivity
(b) High residual flux
(c) Low coercivity
(d) High residual flux and high coercivity

Q4. The pitch factor, in rotating electrical machinery, is defined as the ratio of resultant EMF of a
(a) Full pitch coil to the phase emf
(b) Chorded coil to that of full pitched coil
(c) Full pitched coil to that of a chorded coil
(d) Chorded coil to the phase emf

Q5. What is the maximum load that can be connected in a circuit containing only lighting points?
(a) 500 watts
(b) 750 watts
(c) 800 watts
(d) 1000 watts

Q6. Why are shunt reactors connected at the receiving end of long transmission line system?
(a) To increase the terminal voltage
(b) To compensate for voltage rise caused by capacitive charging at light load
(c) To improve power factor
(d) None of these

S1. Ans.(b)
Sol. Due to the constant core flux, the iron losses also remain constant.

S2. Ans.(a)
Sol. out of all, polarity must be correct for the connected transformers.

S3. Ans.(d)
Sol. both high residual flux, as well as coercivity, is desired for a good permanent magnet.

S4. Ans.(b)
Sol. K_p= Resultant EMF of a chorded coil/Resultant EMF of a full pitched coil = cos⁡(ε/2)

S5. Ans.(c)
Sol. The maximum load that can be connected in a circuit containing only lighting points is 800 watts.

S6. Ans.(b)
Sol. Shunt Reactor compensation at the receiving end help to reduce the effect of capacitance thus reducing the Ferranti effect.

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