Electrical Measurements Questions and Answers Pdf

41. Consider the following statements regarding the controlling torque:

1. It is not present in power factor meter.
2. It opposes the deflecting torque.
3. It is provided by air friction or by fluid friction.

Which of these statements are correct?

(a) 1, 2 and 3.
(b) 1 and 3 only.
(c) 2 and 3 only.
(d) 1 and 2 only.

42. Which of the following statements is correct?

(a) Dynamometer type synchroscope is more commonly used as it is more accurate than moving iron type.
(b) The moving iron synchroscope is more commonly used as it is cheap in cost, robust in construction and suitable for continuous operation.
(c) Weston type synchroscope is more commonly used as it is cheap in cost and robust in construction.
(d) none of the above.

43. Low resistors are provided with four terminals in order to

(a) eliminate the thermoelectric emf effect.
(b) facilitate the connection of current and voltage circuits.
(c) make the resistance value definite irrespective of the nature of contacts at the current terminals.
(d) eliminate the effect of connecting leads.

44. For low resistance (from few micro ohms to one ohm) measurement, which bridge is used ?

(a) Wheatstone bridge.
(b) Kelvin bridge.
(c) Guarded Wheatstone bridge.
(d) Maxwell bridge.

45. Which one of the following bridges will be used for the measurement of very low resistance?

(a) Kelvin bridge.
(b) Maxwell’s bridge.
(c) Wheatstone bridge.
(d) Hay’s bridge.

46. The accuracy of Kelvin’s double bridge for the measurement of low resistance is high because the bridge

(a) uses two pairs or resistance arms.
(b) has medium value resistances in the ratio arms.
(c) uses a low resistance link between standard and test resistances.
(d) uses a null indicating galvanometer.

47. In a Kelvin’s double bridge two sets of readings are taken when measuring low resistance, one with current in one direction and the other with direction of current reversed. This is done to

(a) eliminate the effect of contact resistance.
(b) eliminate the effect of resistance of leads.
(c) correct for the effect of changes in battery voltage.
(d) eliminate the effect of thermoelectric emfs.

48. A Wheatstone bridge cannot be employed for measurement of very low resistance as it introduces error on account of

(a) contact resistance.
(b) resistance of connecting leads.
(c) thermoelectric emfs.
(d) all of the above.

49. In measurement of resistance by Carey Foster bridge no error is introduced due to

(a) contact resistance.
(b) connecting leads.
(c) thermoelectric emfs.
(d) all of these.

50. The sensitivity of a Wheatstone bridge depends upon

(a) galvanometer current sensitivity.
(b) galvanometer resistance.
(c) bridge supply voltage.
(d) all of the above.

51. High resistances are provided with a guard terminal in order to

(a) protect the resistance against stray electrostatic field.
(b) bypass the leakage current.
(c) protect the resistance against overloads.
(d) protect the resistance against stray electromagnetic field.

52. A high resistance cannot be measured by simple ammeter-voltmeter principle because

(a) voltmeter rating will be too high.
(b) ammeter rating will be too low.
(c) leakage current cannot be neglected.
(d) power loss will be high.

53. When a capacitor was connected to the terminal of an ohmmeter the pointer indicated a low resistance initially and then slowly came to infinity position. This shows that the capacitor is

(a) short-circuited.
(b) all right.
(c) open-circuited.
(d) weak.

54. The shunt type ohmmeter is not suitable for high resistance measurements because

(a) very low resistance of the meter would short the high unknown resistance.
(b) scale is highly cramped for high resistance values.
(c) full scale value of the meter may be exceeded.
(d) battery cannot supply the necessary current for proper meter deflection.

55. Which one of the following is measured by the loss of charge method ?

(a) Low R.
(b) High R.
(c) Low L.
(d) High L.

56. Low resistance from few ohms down to one micro-ohm is measured using which one of the following statements ?

(a) Ohmmeter.
(b) A series type ohmmeter.
(c) A shunt type ohmmeter.
(d) A voltmeter and an ammeter.

57. The resistance of a shunt for a precision grade ammeter can be best measured by

(a) De Sauty bridge.
(b) Schering bridge.
(c) Maxwell bridge.
(d) Kelvin double bridge.

58. The Wheatstone bridge method of resistance measurements ideally suitable for the measurement of resistance values in the range of

(a) 0.001 Ω to 1 Ω
(b) 0.1 Ω to 100 Ω
(c) 100 Ω to 10 kΩ
(d) 100 kΩ to 10 MΩ

59. The maximum sensitivity of a Wheatstone bridge is achieved when the bridge

(a) uses dc supply.
(b) uses ac supply.
(c) has unity arm ratio.
(d) has 1 : 2 arm ratio.

60. The potentiometer is standardized for making it

(a) accurate.
(b) precise.
(c) accurate and direct reading.
(d) accurate and precise.