Wattmeter MCQ

1. An induction wattmeter can be used for

  1. both DC and AC
  2. DC only
  3. AC only
  4. none of these
Answer. c

2. Wattmeter can not be designed on the principle of

  1. Electrostatic instrument
  2. Thermocouple instrument
  3. Moving iron instrument
  4. Electrodynamic instrument
Answer. c

3. Wattmeter is of

  1. PMMC type
  2. Dynamometer type
  3. Moving iron type
  4. Hot wire type
Answer. b

4. In a compensated wattmeter, the readings are corrected for errors due to

  1. Power consumed in current coil
  2. Variations in voltage and frequency
  3. Friction
  4. Power consumed in potential coil
Answer. d

5. Poynting-vector wattmeter works on

  1. Magnetic effect
  2. Hall effect
  3. Induction effect
  4. Heating effect
Answer. b

6. In two wattmeter method of measuring power, one of the wattmeters reads zero watts. The power factor of the load is

  1. Unity
  2. 0.8
  3. 0.5
  4. 0.6
Answer. c

7. While measuring power by two wattmeter method, the phase voltage is 3 V whereas the phase current is 0.5A. If the angle between phase current and phase voltage is 30 degrees, the total power consumed by the load will be

  1. 3.125 W
  2. 1.11 W
  3. 2.25 W
  4. 2.57 W
Answer. c

8. A dynamometer type of wattmeter responds to

  1. R.M.S value of active power
  2. Average value of active power
  3. Average value of reactive power
  4. R.M.S value of reactive power
Answer. b

9. A wattmeter is being tested under phantom-loading condition. If the wattmeter reading is 60W, the actual power consumed from the supply is

  1. Much higher than 60W
  2. 60W
  3. Much less than 60W
  4. 30W
Answer. c

10. In dynamometer wattmeter the compensation coil

  1. Has equal number of voltage coil and is connected in series with current coil
  2. Has equal number of turns of current coil and is connected in series with voltage coil
  3. Has equal number of current coil and is connected in series with current coil
  4. Has equal number of voltage coil and is connected in series with voltage coil
Answer. b

11. Which power factor results in equal reading of both wattmeter in 2 wattmeter method?

  1. Unity
  2. Half
  3. Zero
  4. None of the above
Answer. a

12. At which angle in two wattmeter method, one wattmeter show zero readings

  1. Φ = 0°
  2. Φ = 60°
  3. Φ = 90°
  4. Φ = 45°
Answer. b

13.Which of the following is not a method of resistance measurement?

  1. Ammeter-voltmeter method
  2. Post-office box method
  3. Ohm-meter method
  4. Two wattmeter method
Answer. d

14. Three wattmeter method of power measurement can be used to measure power in

  1. Both balanced and unbalanced circuits
  2. Balanced circuits
  3. None of the options
  4. Unbalanced circuits
Answer. a

15. The moving coil in a dynamometer wattmeter is connected

  1. In series with the fixed coil
  2. Across the supply
  3. In series with the load
  4. Any one of the above
Answer. b

16. A dynamometer type wattmeter responds to the

  1. Average value of active power
  2. Average value of reactive power
  3. Peak value of active power
  4. Peak value of reactive power
Answer. a

17. Two meters X and Y required 40 mA and 50 mA respectively for full-scale deflection. Then

  1. Both are equally sensitive
  2. Data are insufficient to comment
  3. X is more sensitive than Y
  4. Y is more sensitive than X
Answer. c

18. In the measurement of power in a balanced 3-phase circuit by two wattmeter method if the two wattmeters show equal readings. Then the power factor of the circuit is

  1. Zero
  2. Unity
  3. 0.8 lagging
  4. 0.8 leading
Answer. b

19. A wattmeter is marked 15A/30A, 300V/600V and its scale is marked up to 4500 watts. When the meter is connected for 30A, 600V, the point indicated 2000 watts. The actual power in the circuit is

  1. 2000 watts
  2. 4000 watts
  3. 6000 watts
  4. 8000 watts
Answer. d

20. The power in an unbalance 3-phases 4-wire circuit can be measured by using a _______ method.

  1. 4 Wattmeter
  2. 3 wattmeter
  3. 2 wattmeter
  4. 1 wattmeter
Answer. b