41. The resolution of a potentiometer should be
(a) infinite.
(b) very high.
(c) medium.
(d) zero.
Answer: (c) medium.
42. Which one of the following statements for a potentiometric transducer is correct?
(a) It is a zero order displacement transducer.
(b) It is a first order displacement transducer.
(c) It is a zero order temperature transducer.
(d) It is a second order displacement transducer.
Answer: (a) It is a zero order displacement transducer.
43. A strain gauge is passive transducer and is employed for converting
(a) mechanical displacement into a change of resistance.
(b) pressure into a change of resistance.
(c) force into displacement.
(d) none of the above.
Answer: (a) mechanical displacement into a change of resistance.
44. The sensitivity factor of strain gauge is normally of the order of
(a) 1 to 1.5
(b) 1.5 to 2.0
(c) 0.5 to 1
(d) 5 to 10
Answer: (b) 1.5 to 2.0
45. In wire wound strain gauges, the change in resistance under strained condition is mainly on account of
(a) change in diameter of wire.
(b) change in length of wire.
(c) change in both length and diameter of wire.
(d) change in resistivity.
Answer: (c) change in both length and diameter of wire.
46. Bonded strain gauges are
(a) exclusively used for construction of transducers.
(b) exclusively used for stress analysis.
(c) used for both stress analysis and for construction of transducers.
(d) none of the above.
Answer: (c) used for both stress analysis and for construction of transducers.
47. Over wire strain gauges foil strain gauges have the advantages of
(a) higher heat dissipation capacity and better bonding.
(b) superior mechanical stability under prolonged strained and high temperature conditions, low hysteresis and creeping effects.
(c) excellent reproducibility and longer life.
(d) all of the above.
Answer: (d) all of the above.
48. Which of the following is not an advantage of semiconductor gauges as compared to conventional strain gauges.
(a) Excellent hysteresis characteristics.
(b) Least sensitive to temperature changes.
(c) High fatigue life.
(d) Smaller size.
Answer: (b) Least sensitive to temperature changes.
49. In semiconductor strain gauges, what happens when a tensile strain is applied?
(a) Resistance increases in N-type of materials.
(b) Resistance increases in P-type of materials.
(c) Resistance increases in both P and N-type of materials.
(d) Resistance decreases in both P and N-type of materials.
Answer: (b) Resistance increases in P-type of materials.
50. The drawbacks of strain gauges are
(a) low fatigue life.
(b) that they are expensive, brittle, highly sensitive to temperature variations.
(c) poor linearity.
(d) that they are prone to hysteresis and creep effects.
(e) both (b) and (c).
Answer: (e) both (b) and (c).
51. Semiconductor of strain gauges are made of
(a) silicon.
(b) gold.
(c) silver.
(d) nickel.
Answer: (a) silicon.
52. The wire material of strain gauges should have
(a) high resistivity and high thermo-emfs.
(b) low resistivity and high thermo-emfs.
(c) low resistivity and low thermo-emfs.
(d) high resistivity and low thermo-emfs.
Answer: (d) high resistivity and low thermo-emfs.
53. The strain gauges should have low
(a) gauge factor.
(b) resistance temperature coefficient.
(c) resistance.
(d) all of the above.
Answer: (b) resistance temperature coefficient.
54. The carrier material employed with strain gauges at room temperature is
(a) impregnated paper.
(b) bakelite.
(c) epoxy.
(d) aluminum foil.
Answer: (a) impregnated paper.
55. A rosette gauge is used to determine
(a) principal stress direction only.
(b) principal strain direction only.
(c) principal stress or strain direction and magnitude.
(d) principal strain direction and magnitude.
Answer: (c) principal stress or strain direction and magnitude.
56. Rosette gauges are employed for measuring
(a) strain in a direction.
(b) variable strain.
(c) strain in more than one direction.
(d) small strains.
Answer: (c) strain in more than one direction.
57. Platinum is the commonly used metal for resistance-temperature detectors (RTDs) because
(a) it is commercially available in pure form at reasonable rates.
(b) it is relatively stable under various environment conditions.
(c) it has wide operating temperature range.
(d) all of the above.
Answer: (d) all of the above.
58. RTDs have
(a) positive temperature coefficient.
(b) negative temperature coefficient.
(c) either type of temperature coefficient.
(d) high tolerance.
Answer: (a) positive temperature coefficient.
59. The V-I characteristics of a thermistor exhibits a negative resistance region. This statement is
(a) true.
(b) false.
(c) true for NTC thermistor (negative temperature coefficient).
(d) true for PTC thermistor (positive temperature coefficient.
Answer: (c) true for NTC thermistor (negative temperature coefficient).
60. Consider the following statements in connection with measurement of temperature :
- A thermistor is highly sensitive as compared with platinum resistance thermometer.
- The resistance of a thermistor is solely a function of its absolute temperature whether the source of heat is external, internal or both.
- A thermistor has linear resistance temperature characteristics.
- Most thermistors exhibit negative resistance temperature coefficient. Which of these statements are correct ?
(a) 1, 2 and 3.
(b) 1, 2 and 4.
(c) 2, 3 and 4.
(d) 1, 3 and 4.
Answer: (b) 1, 2 and 4.