Wattmeter MCQ

51. The power of 6-phase circuit can be measured with a minimum of

  1. 1 wattmeter
  2. 5 wattmeter
  3. 3 wattmeter
  4. 6 wattmeter
Answer
Answer. b

52. A 3-phase balanced supply system is connected to a 3-phase unbalance load. Power supplied to this load can be measured using

  1. two wattmeters
  2. one wattmeter
  3. three wattmeters

Which of these statements is/are correct?

  1. 1 & 2
  2. 1 & 3
  3. 2 & 3
  4. 3 & alone
Answer
Answer. b

53. Which of the following is not a type of wattmeter?

  1. Moving coil permanent magnet
  2. Induction
  3. Dynamometer
  4. Electrostatic
Answer
Answer. a

54. Measurement of power of a 3-phase balanced load is done using two wattmeter method. If the ratio of the wattmeter readings is 2:1 then the power factor of the circuit will be

  1. 0
  2. 1
  3. 0.5
  4. 0.866
Answer
Answer. d

55. In the two wattmeter method of measuring 3-phase power, the wattmeter indicated equal and opposite readings when the load power factor is

  1. 90° leading
  2. 90° lagging
  3. 30° leading
  4. 30° lagging
Answer
Answer. b

56. The current and potential coils of a dynamometer type wattmeter were accidentally interchanged while connecting. After energizing the circuit, it was observed that the wattmeter did not show the reading. This could be due to

  1. Damage to potential coils
  2. Damage to current coil
  3. Damage to both current coil and pressure coil
  4. Loose contacts
Answer
Answer. b

57. In the measuremènt of three-phase power by two wattmeter method, if the two wattmeter readings are equal then the power factor of the circuit is

  1. 0.8 lag
  2. Unity
  3. 0.8 lead
  4. Zero
Answer
Answer. b

58. The power in a 3-phase circuit is measured with the help of 2 wattmeters. The reading of one of the wattmeters is positive and that of the others is negative. The magnitude of readings is different. It can be concluded that the power factor of the circuit is

  1. Unity
  2. 2 (lagging)
  3. 5 (lagging)
  4. less than 0.5 (lagging)
Answer
Answer. d

59. Which type of wattmeter can not be used for both A.C. & D.C.?

  1. Dynamometer type
  2. Electrostatic type
  3. Induction type
  4. None of the above
Answer
Answer. c

60. Which of the following material will be prefered as a shunt for extending the range measurement of a voltmeter?

  1. Copper
  2. Steel
  3. Aluminium
  4. Manganin
Answer
Answer. d
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