(b) frost-free refrigerators
     (c) sub-marine propulsion
     (d) researches in superconductivity
Ans : (a)
42. Which of the following take place when the subject speaks untruth while being tested by the polygraph instrument? [CDS1993]
       1) His blood pressure goes up.
       2) His pulse quickens
       3) His skin darkens
       4) He sneezes.
       (a) 1and 2
       (b) 3 and 4
       (c) 1, 2 and 3
       (d) 2, 1and 3
Ans : (a)
43. If 5 denotes sound energy, E denotes electrical energy and M denotes magnetic energy, the correct representation of recording and
     reproduction in an audio tape recorder is : [IAS 1988]
       (a) S → M → E → M → S
       (b) S → E → M → E → S
       (c) E → S → M → S
       (d) E → M → E → S
Ans : (b)
44. In a refrigerator, cooling is produced by:
       (a) the ice which deposits on the freezer
       (b) the sudden expansion of a compressed gas
       (c) the evaporation of a volatile liquid
       (d) None of the above
Ans : (c)
45. The best colour(s) for a sun umbrella will be: [CDS 1989]
       (a) black
       (b) black on top and white on the inside
       (c) white on top and black on the inside
       (d) printed with all the seven colours of rainbow
Ans : (c)
46. Which of the following laws is explained by the statement that matter can neither be created for destroyed? [I.Tax & Central
     Excise 1989]
       (a) Law of Conservation of Energy
       (b) Le Chatelier"s principle
       (c) Law of Conservation of Mass
       (d) Law of Osmosis
Ans : (c)
47. The mass-energy relation is the outcomes of: [IAS 1989]
       (a) quantum theory
       (b) general theory of relativity
       (c) field theory of energy
       (d) special theory of relativity