NHPC-JE'21 EE: Daily Practices Quiz 12-NOV-2021

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NHPC-JE’21 EE: Daily Practices Quiz

NHPC-JE’21 EE: Daily Practices Quiz 12-NOV-2021

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

Q1. A generating station has a maximum demand of 35 MW and has a connected load of 60 MW. What will be the demand factor?
(a) 0.583 %
(b) 5.83 %
(c) 0.0583 %
(d) 58.3 %

Q2. In a DC machine, how are the commutating pole winding connected?
(a) In series with the shunt winding
(b) Parallel to the shunt winding
(c) In series with the armature winding
(d) Parallel to the armature winding

Q3. In an induction motor, if the rotor resistance is equal to stand-still reactance then the maximum torque is…………
(a) Less than starting torque
(b) Equal to starting torque
(c) More than starting torque
(d) None of the above

Q4. Reactance relay is used for protection in:
(a) Long transmission lines
(b) Short transmission lines
(c) Medium transmission lines
(d) Both long transmission lines and short transmission lines

Q5. A supply voltage of 230 V, 50 Hz is fed to a residential building. Write down its equation for instantaneous value.
(a) 163 sin 314·16 t
(b) 230 sin 314·16 t
(c) 325 sin 314·16 t
(d) 361sin314·16 t

Q6. The AC bridge used for measurement of dielectric loss of capacitor is
(a) Anderson bridge
(b) Schering bridge
(c) Wien bridge
(d) Hay’s bridge

SOLUTIONS

S1. Ans.(d)
Sol. Demand factor=maximum demand/connected load =35/60=0.583 or 58.3 %.

S2. Ans.(c)
Sol. commutating pole winding is connected in series with the armature winding in order to cancel the armature reaction.

S3. Ans.(b)
Sol. At maximum torque: slip(s)=R_2/X_2
If R_2=X_2, then s=1(starting slip)
So, if in an induction motor, if the rotor resistance is equal to stand-still reactance then the maximum torque is equal to starting torque.

S4. Ans.(b)
Sol. Relay used for different configuration of transmission lines……
Short transmission line: reactance relay
Medium transmission line: impedance relay
Long transmission line: mho relay

S5. Ans.(c)
Sol. V=V_m sin⁡(2πft)=230×√2 sin⁡(2×3.14×50 t)=325 sin⁡(314 t)

S6. Ans.(b)
Sol. Schering bridge is used for measurement of dielectric loss of capacitor.