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Saturday, 16 January 2016

Electrical Measuring instruments - Multiple Choice Questions

Electrical Measuring instruments - Multiple Choice Questions Points : electrical measuring instruments, multiple choice questions and answers, electrical objective type question answers, mcqs 1. Permanent-magnet moving coil instrument can be use for .......
(i) a.c. work only
(ii) d.c. work only
(iii) both d.c. and a.c. work
(iv) none of above

2. In eddy current damping, disc or former is prepared of a material that is a ………….
(i) conductor but non-magnetic
(ii) conductor but magnetic
(iii) non-conductor and non-magnetic
(iv) non-conductor but magnetic

3. An ammeter is …….. instrument.
(i) an indicating
(ii) an integrating
(iii) a recording
(iv) none of the above

4. When indicator of an indicating instrument comes to rest in the ending deflected place ………
(i) only controlling torque acts
(ii) only deflecting torque acts
(iii) both deflecting and controlling torques act
(iv) none of above

5. A small swamping resistance is put in series with operating coil of a affecting coil ammeter in order to compensate for the effects of …………..
(i) temperature variation
(ii) external magnetic fields
(iii) hysteresis loss
(iv) none of the above

6. The range of a permanent-magnet moving coil instrument is 0-10 A. If the full- scale deflection current of the meter is 2 mA, then multiplying power of shunt is ………….
(i) 2500
(ii) 10000
(iii) 5000
(iv) none of the above

7. The pointer of an indicating instrument is usually prepared of ..............
(i) copper
(ii) aluminum
(iii) silver
(iv) soft steel

8. A moving coil instrument have meter resistance of 5 Ω is to be use as a voltmeter of range 0-100 V. If the full-scale deflection current is 10 mA, then necessary series resistance is ………..
(i) 20Ω
(ii) 1000Ω
(iii) 9995Ω
(iv) none of the above

9. The material of the shunt should have …………. temperature co-efficient of opposition.
(i) negligible
(ii) positive
(iii) negative
(iv) none of the above

10. In common, fluid friction damping is not working in indicating instruments while one can find its use in ………….
(i) dynamometer wattmeter
(ii) hot-wire ammeter
(iii) induction type energy meter
(iv) kelvin electrostatic voltmeter

11. The calculating torque of an indicative of instrument ………. as deflection of moving system increase.
(i) remains unchanged
(ii) decreases
(iii) increases
(iv) none of the above

12. The mutliplying power of shunt of a milliammeter is 8. If circuit current is 200 mA, then current through the meter is ……………..
(i) 200 mA
(ii) 25 mA
(iii) 1600 mA
(iv) none of the above

13. A moving coil voltmeter gives full-scale deflection of 100 V for a meter current of 1 mA. For 45 V reading, meter current will be .........
(i) 0.45 mA
(ii) 1.45 mA
(iii) 2.22 mA
(iv) none of the above

14. Moving-iron instruments have ……….. scale.
(i) uniform
(ii) squared
(iii) log
(iv) none of the above

15. The scale of a permanent-magnet moving coil instrument is even as …………
(i) of effective eddy current damping
(ii) external magnetic fields have no result
(iii) it is spring controlled
(iv) it has no hysteresis loss

16. Hot-wire instruments contain ......… scale.
(i) uniform
(ii) log
(iii) squared
(iv) none of the above

17. When pointer of an indicating instrument is in final deflected place ………..
(i) deflecting torque is zero
(ii) controlling torque is zero
(iii) damping torque is zero
(iv) both deflecting & controlling torques are zero

18. An electric pyrometer is an instrument use to calculate ……….
(i) phase
(ii) frequency
(iii) high temperatures
(iv) none of the above

19. When pointer of an indicating instrument is in motion then deflecting torque is opposite through ………
(i) controlling torque simply
(ii) damping torque only
(iii) both damping and controlling torque
(iv) none of the above

20. For measure high values of alternating current by a dynamometer ammeter, we utilize a ………..
(i) shunt
(ii) multiplier
(iii) potential transformer
(iv) current transformer

21. Shunts are usually made of ……………
(i) copper
(ii) aluminum
(iii) silver
(iv) manganin

22. Dynamometer kind ……… has consistent scale.
(i) ammeter
(ii) wattmeter
(iii) voltmeter
(iv) none of the above

23. Dynamometer kind instruments can be use of ………
(i) a.c. work only
(ii) d.c. work only
(iii) for both d.c. and a.c. work

(iv) none of the above 24. In adynamometer type instrument, damping is provide through ………
(i) air friction
(ii) eddy currents
(iii) fluid friction
(iv) none of the above

25. The range of a moving-iron a.c. ammeter is extensive by ………….
(i) a shunt
(ii) a multiplier
(iii) c hanging number of turns of operating coil
(iv) none of the above

26. ………….. movement is mainly expensive.
(i) D’Arsonval movement
(ii) Moving-iron
(iii) Dynamometer
(iv) none of the above

27. Electrostatic instruments are use as ………….
(i) voltmeters only
(ii) ammeters only
(iii) both ammeters and voltmeters
(iv) wattmeters only

28. If current through the operating coil of a moving-iron instrument is doubled, the operating force becomes ………..
(i) two times
(ii) four times
(iii) one-halftime
(iv) three times

29. The instrument in which springs provide the controlling torque as well as serve to lead current into and out of the working coil is …..... instrument.
(i) -moving-iron
(ii) hot-wire
(iii) permanent-magnet moving coil
(iv) none of the above

30. To calculate high-frequency currents, we generally use ………… ammeter.
(i) hot-wire
(ii) dynamometer
(ii.) moving-iron
(iv) thermocouple

31. A dynamometer instrument is mainly use as a ……….
(i) d.c. ammeter
(ii) d.c. voltmeter
(iii) wattmeter
(iv) none of the above

32. Full-scale deflection current of a moving coil instrument is about …………
(i) 50 mA
(ii) 1 A
(iii) 3 A
(iv) 2 A

33. All voltmeters except ……….. voltmeters are operate through the passage of current.
(i) moving-iron
(ii) electrostatic
(iii) dynamometer
(iv) permanent-magnet moving coil

34. The most usually use induction type instrument is …………..
(i) induction voltmeter
(ii) induction wattmeter
(iii) induction watt-hour meter
(iv) induction ammeter

35. The watt-hour meter is ………. instrument.
(i) an integrating
(ii) an indicating
(iii) a recording
(iv) a transfer

36. The full scale voltage across a moving coil voltmeter is on …………
(i) 10 V
(ii) 5V
(iii) 100 V
(iv) 50 mV

37. ………… meter will be the most sensitive.
(i) 50 mA
(ii) 100 μA
(iii) 50 A
(iv) 1 μA

38. On a simple ohmmeter, the 0 Ω mark is ………… of the scale.
(i) far left
(ii) far right
(iii) in the middle
(iv) none of the above

39. If a wattmeter connected in circuit gives down scale reading, then we normally change connections of
(i) current coil
(ii) potential coil
(iii) both current and potential coils
(iv) none of above

40. For measurement of high direct voltage (say 10 kV), one would use …….. voltmeter.
(i) permanent-magnet moving coil
(ii) electrostatic
(iii) hot-wire
(iv) moving iron

41. The best type of meter movement is …….. movement.
(i) iron-vane
(ii) D’Arsonval
(iii) dynamometer
(iv) none of the above

42. In Induction kind ammeter, ............... damping is provided.
(i) air friction
(ii) eddy current
(iii) fluid friction
(iv) none of the above

43. ......... instruments are the majority sensitive.
(i) moving-iron
(ii) hot-wire
(iii) dynamometer
(iv) permanent-magnet moving coil

44. Indicating instruments are assumed to be the majority accurate ………. part of scale.
(i) at beginning
(ii) at finishing
(iii) at half of full
(iv) none of the above

45. A permanent magnet moving coil ammeter is attached in 50 Hz a.c. circuit in which 5A current is flowing. The meter will read
(i) 0A
(ii) 5A
(iii) 2.5 A
(iv) none of above

46. Resistance of an ammeter having range 0-5A is 1.8Ω. It is shunted by a resistor of 0.2Ω. What is the effective current when the pointer reads 2 A ?
(i) 10 A
(ii) 30 A
(iii) 15 A
(iv) 20 A

47. In a single phase energy meter, braking torque is provided by
(i) permanent magnet
(ii) air friction
(iii) fluid friction
(iv) none of above

48. When the terminals of a series ohmmeter are open-circuited the pointer reads
(i) zero
(ii) infinity
(iii) a high resistance
(iv) none of above

49. An energy meter whose meter constant is 1500 rev/kWh makes 20 revolutions in 30 seconds. The load in kW is
(i) 32kW
(ii) 08kW
(iii) 64 kW
(iv) 16 kW

50. On a simple ohmmeter, the infinity Ω mark is …….. of the scale.
(i) far left
(ii) far right
(iii) in the middle
(iv) none of above

51. In a dynamometer wattmeter, the moving coil is the
(i) current coil
(ii) potential coil
(iii) current coil or potential coil
(iv) none of the above

52. Induction wattmeter can measure
(i) a.c. power only
(ii) d.c. power only
(iii) both a.c. and d.c. power
(iv) none of above

53. The instrument used in an ohmmeter is generally
(i) moving-iron type
(ii) hot-wire type
(iii) permanent magnetic moving coil type
(iv) Dynamometer type

54. Out of the following, the most accurate measurement of unknown resistance will be by
(i) potentiometer
(ii) ohmmeter
(iii) voltmeter and ammeter
(iv) wheatstone bridge

55. The scale of an ohmmeter is
(i) linear
(ii) non-linear
(iii) linear and non-linear
(iv) none of above

56. A 230 V, 50 Hz single-phase energy meter has a load current of 10 A a p.f. of 0.8 lagging. The energy consumed by the load in 2 minutes is
(i) 1.2 kWh
(ii) 006 kwh
(iii) 24 kWh
(iv) 42 kWh

57. To measure a.c. as well as d.c. power, we use
(i) induction wattmeter
(ii) dynamometer wattmeter
(iii) sometimes induction and sometimes dynamometer wattmeter
(iv) none of above

58. The meter constant of an energy meter is 1500 rev/kWh, the disc makes 3000 revolutions in a given time. The energy consumed is
(i) 4 kWh
(ii) 1 kWh
(iii) 3 kWh
(iv) 2 kWh

59. In a single phase energy meter, if the brake magnet is moved towards the centre of the spindle, the disc speed
(i) increases
(ii) decreases
(iii) remains same
(iv) none of above

60. If the full-scale current of a meter is 50 μA, then its sensitivity is
(i) 1000 Ω/V
(ii) 20,000 Ω/V
(iii) 10,000 Ω/V
(iv) data insufficient

88. A 100 V. full-scale, 100 Ω volt meter has a full-scale deflection current of
(i) 0.5 mA
(ii) 2 mA
(iii) 3.5 mA
(iv) 1 mA

61. A moving coil galvanometer has a sensitivity of 60 divisions/amp. When a shunt is used its sensitivity becomes 10 div amp. What is the value of the shunt used if the resistance of the galvanometer is 20 Ω?
(i) Ω 2
(ii) 6 Ω
(iii) 4 Ω
(iv) 1 Ω

62. Which of the following is likely to have the largest resistance?
(i) moving coil galvanometer
(ii) voltmeter of range 10 V
(iii) ammeter of range I A
(iv) a copper wire of length 1 m and diameter 3 mm

63. If 2 % of the main current is o be passed through a moving coil galvanometer of resistance G. the resistance of the shunt required is
(i) G/49
(ii) G/50
(iii) 49G
(iv) 50 G

64. The sensitivity of a moving coil galvanometer is 60 divisions/ampere. When a shunt is used, the sensitivity becomes 10 divisions/ampere. If the galvanometer resistance is 20 Ω, the value of shunt is
(i) 15 Ω
(ii) 20 Ω
(iii) 4 Ω
(iv) 5 Ω

65. In a moving coil galvanometer, the deflection becomes one-half when the galvanometer is shunted by a 20 Ω resistor. The galvanometer resistance is
(i) 10 Ω
(ii) 40 Ω
(iii) 20Ω
(iv) 5 Ω

66. Deflection of a moving coil galvanometer falls from 50 divisions to 20 divisions when a 12 Ω shunt is applied. Galvanometer resistance is
(i) 18 Ω
(ii) 6 Ω
(iii) 9 Ω
(iv) 24 Ω

67. A series ohmmeter circuit uses a 3 V battery and 1 mA meter movement. What is the half scale resistance for this ohmmeter?
(i) 6 kΩ
(ii) 1.5kΩ
(iii) 12 kΩ
(iv) 3 kΩ

68. To send 10 % of main current through a moving coil galvanometer of resistance 99 Ω the value of shunt resistance required is
(i) 33 Ω
(ii) 9.9 Ω
(iii) 22 Ω
(iv) 11 Ω

69. A 10 V range voltmeter is rated for 50 μA full-scale current. The total resistance of the voltmeter is
(i) 100 kΩ
(ii) 200 kΩ
(iii) 300 kΩ
(iv) 400 kΩ

70. A 20 μA. 200 mV meter movement is used to make a 25 V voltmeter. What is the sensitivity of the meter?
(i) 25 kΩ/V
(ii) 50 kΩ/V
(iii) 100 kΩ/V
(iv) 75 kΩ/V

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