## Wednesday, April 24, 2019 # Physics MCQs of WBCS Prelims Previous Years Questions P16

Physics - 16

76. If the length and cross-section of a Wire are both doubled, the resistance will
(A) Increase twice
(B) Remain unchanged
(C) Increase 4 times
(D) Decrease 5 times

77. A solid piece of iron sinks in water but floats in mercury because -
(A) the density of iron is more than that of water as well as mercury
(B) the density of iron is more than that of water but less than that mercury
(C) the average density of water & mercury is less than that of iron
(D) the density of iron is less than that of water as well as mercury

Correct Answer: [B] the density of iron is more than that of water but less than that mercury.
78. When the water cools from 7°C to 0°C
(A) It first contracts and then expands
(B) It first expands and then contracts
(C) It contracts only
(D) It expands only

Correct Answer: [A] It first contracts and then expands.
79. When a positively charged conductor is earthed, then
(A) Electrons flow from the earth to the conductor
(B) Protons flow from the earth to the conductor
(C) Electrons flow from the conductor to the earth
(D) Protons flow from the conductor to the earth

Correct Answer: [A] Electrons flow from the earth to the conductor.