141) During rusting
(A) Iron gains weight
(B) Iron loses weight
(C) Weight of iron remains unchanged
(D) Iron volatilizes
142) When water boils, its temperature
(A) Begins to increase
(B) Begins to decrease
(C) Remains constant
(D) Fluctuates
143) Rectifiers are used to convert
(A) DC to AC
(B) AC to DC
(C) High voltage to low voltage
(D) Low voltage to high voltage
144) A needle smeared with vaseline when lowered slowly on the surface of water in a horizontal position appears to float. The phenomenon is an example of
(A) Capillary action
(B) Surface tension
(C) Osmosis
(D) Archimedes' principle
145) Which one of the following statements is correct?
A slab of ice kept in a room
(A) Does not radiate heat
(B) Does not radiate heat but absorbs heat from the surrounding
(C) Radiates heat but absorbs more heat from the surrounding
(D) Radiates heat more than that absorbed by it from the surrounding
146) The phenomenon of formation of three dimensional image by interference of two light beams from laser or other coherent sources of light is called:
(A) Optical photography
(B) X-ray photography
(C) Radiography
(D) Holography
147) Paper becomes brittle and yellow with age. Why?
1. The acid content in paper causes brittleness to develop
2. In the presence of visible light, photosensitized oxidation occurs
3. Tho ultra-violet component of sunlight causes photolysis of cellulose by direct cleavage of the cellulose polymer
(A) 1 and 2
(B) 2 and 3
(C) 1 and 3
(D) 1, 2 and 3
148) Two cars, passing each other at high speed, are in danger of side swiping because
(A) Of the increase in air pressure in the space between them
(B) Of decrease in the velocity of air molecules between them
(C) Of decrease in air pressure in the space between them
(D) Increase in the velocity of air molecules between them
149) Which of the following is used as a coolant In nuclear reactors?
(A) Heavy water
(B) Cadmium
(C) Liquid sodium
(D) Graphite
150) Which of the following is good nuclear fuel?
(A) Uranium-238
(B) Neptunium-239
(C) Thorium-236
(D) Plutonium-239