E-PolyLearning

41. An alloy of Fe - 0.4 % C is
a. cast iron.
b. hypo-eutectoid steel.
c. hyper-eutectoid steel.
d. eutectoid steel
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Answer: (b).hypo-eutectoid steel.

42. A material in which the atoms are arranged regularly in some directions but not in others, is termed as 'mesomorphous material'; an example of which is
a. lead
b. glass
c. mica
d. silver
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Answer: (a).lead

43. Maximum amount of thermal radiation is emitted at all wavelengths at any specified temperature by a/an __________ body.
a. grey
b. black
c. opaque
d. white
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Answer: (a).grey

44. In condensers used in thermal power plants, steam is normally used in shell side and cooling water on the tube side, because of the reason that
a. compared to the mass flow rate of cooling water, the rate of condensation of steam is invariably smaller.
b. maintaining vacuum on tube side is more difficult than that on the shell side.
c. water velocity can be increased conveniently to increase the overall heat transfer co-efficient because of its lower specific volume compared to steam.
d. condenser can act as a storage unit for condensed steam.
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Answer: (c).water velocity can be increased conveniently to increase the overall heat transfer co-efficient because of its lower specific volume compared to steam.

45. Cobalt - 60 is used as a source of __________ in medical therapy & industrial radiography.
a. X-rays
b. γ-rays
c. α-rays
d. β-rays
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Answer: (b).γ-rays