NHPC-JE’21 EE: Daily Practices Quiz 04-Oct-2021

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NHPC-JE’21 EE: Daily Practices Quiz

NHPC-JE’21 EE: Daily Practices Quiz 04-Oct-2021

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

Q1. The torque in an induction motor varies as _______________
(a) square of voltage
(b) proportion to voltage
(c) inversely proportion to the voltage
(d) none of the above

Q2. For the satisfactory performance of 3-phase 480V, 60 Hz induction motor, the supply voltage at 50 Hz should be equal to
(a) 480 V
(b) 350 V
(c) 400 V
(d) 420 V

Q3. In the circuit given below, determine Vab.

(a) 2.5 V
(b) 3.5 V
(c) 7 V
(d) 5V

Q4. The type of single-phase induction motor having the highest power factor at full load is:
(a) Shaded pole type
(b) Split-phase type
(c) Capacitor-start type
(d) Capacitor-run type

Q5. In house wiring, Black and Green wires indicate
(a) Earth and neutral respectively
(b) Phase and neutral respectively
(c) Phase and earth respectively
(d) Neutral and earth respectively

Q6. In a power plant if the maximum demand on the plant is equal to the plant capacity, then
(a) Load factor will be nearly 60%
(b) Plant reserve capacity will be zero
(c) Diversity Factor will be unity
(d) Load factor will be unity

SOLUTIONS

S1. Ans.(a)
Sol. Torque in induction motor varies as the square of the voltage.

S2. Ans.(c)
Sol. For satisfactory performance, the V / f ratio must be constant.

S3. Ans.(b)
Sol. Nodal analysis at point a: (Va-1)/2+Va/2-3=0
∴2Va=7
⇒Va=3.5=Vab

S4. Ans.(d)
Sol. capacitor-run type motor will have high power factor in which capacitor will be connected in running condition.

S5. Ans.(d)
Sol. In house wiring, Black and Green wires indicate neutral and earth respectively.

S6. Ans.(b)
Sol. Reserve capacity = Plant capacity – Max. Demand
If the plant capacity is equal to Max. Demand, then the Reserve capacity will be zero.

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