Questions and answers for exam Preparation

MCQs

Total Questions : 103 | Page 1 of 11 pages

Question 1. In some energy meters, creeping can be avoided by __________

attaching small gold pieces
attaching small aluminium pieces
attaching small iron pieces
attaching small zinc pieces

Discuss Question

Answer: Option C. -> attaching small iron pieces
Answer: (c).attaching small iron pieces

Question 2. Creeping is avoided by __________

reversing the polarity of the voltage
drilling two diametrically opposite holes
holding the disc
increasing the friction

Discuss Question

Answer: Option B. -> drilling two diametrically opposite holes
Answer: (b).drilling two diametrically opposite holes

Question 3. Measurement of energy involves _________

inductance and capacitance measurement
power consumption and time duration
resistance measurement and voltage drop
current consumption and voltage drop

Discuss Question

Answer: Option B. -> power consumption and time duration
Answer: (b).power consumption and time duration

Question 4. An electronic energy meter makes use of ___________

IC
Transformer
CRO
Multimeter

Discuss Question

Answer: Option A. -> IC
Answer: (a).IC

Question 5. Average power is _________

product of voltage and current
product of average current and voltage
product of instantaneous voltage and current
product of absolute voltage and current

Discuss Question

Answer: Option C. -> product of instantaneous voltage and current
Answer: (c).product of instantaneous voltage and current

Question 6. Choose the correct statement regarding two watt-meter method for power measurements in 3-phase circuit.

When power factor is unity, one of the wattmeters reads zero
When the readings of the two watt-meters are equal but opposite sign, the power factor is zero
Power can be measured using two watt-meter method only for star connected 3-phase circuit
When two watt-meters show identical readings, the power factor is 0.5

Discuss Question

Answer: Option B. -> When the readings of the two watt-meters are equal but opposite sign, the power factor is zero
Answer: (b).When the readings of the two watt-meters are equal but opposite sign, the power factor is zero

Question 7. The meter constant of a single-phase, 230 V induction watt-meter is 600 rev/kW-h. The speed of the meter disc for a current of 15 A at 0.8 power factor lagging will be?

30.3 rpm
25.02 rpm
27.6 rpm
33.1 rpm

Discuss Question

Answer: Option C. -> 27.6 rpm
Answer: (c).27.6 rpm

Question 8. In the measurement of 3-phase power by 2 watt-meter method, if the 2 watt-meter readings are equal, the power factor of the circuit is?

0.8 lagging
0.8 leading
Zero
Unity

Discuss Question

Answer: Option D. -> Unity
Answer: (d).Unity

Question 9. A coil (which can be modelled as a series RL circuit) has been designed for high Q performance. The voltage is rated at and a specified frequency. If the frequency of operation is increased 10 times and the coil is operated at the same rated voltage. The new value of Q factor and the active power P will be?

P is doubled and Q is halved
P is halved and Q is doubled
P remains constant and Q is doubled
P decreases 100 times and Q is increased 10 times

Discuss Question

Answer: Option D. -> P decreases 100 times and Q is increased 10 times
Answer: (d).P decreases 100 times and Q is increased 10 times

Question 10. Two watt-meters, which are connected to measure the total power on a three-phase system supplying a balanced load, read 20.5 kW and -3.5 kW respectively. The total power is?