91) Why does water boil below 100°C at higher altitudes?
(A) There is lesser dissipation of heat at higher altitudes
(B) Water available at higher altitude is purer than that in the plains
(C) Pollution-free air at higher altitude increases the calorific value of fuel used
(D) The atmospheric pressure at higher altitude is low as compared to that at sea level
92) The speed of sound is maximum through which of the following?
93) Echo Is the effect produced due to
(A) Absorption of sound
(B) Dispersion of sound
(C) Reflection of sound
(D) Refraction of sound
94) In a photographic camera fitted with a convex lens, which of the following types of images will be formed on the film?
(A) Erect and real
(B) Inverted and real
(C) Imaginary and erect
(D) The type of image formed will depend on the distance between lens and the object
95) In the modern-day computers, when operational, the electrical impulses travel
(A) At the speed of sound
(B) At seven times the speed of sound
(C) At half the speed of light
(D) At the speed of light
96) A magnet freely suspended by means of a string will always set itself in which of the following directions?
97) Why are shields made of iron usually provided around precision instruments?
(A) For protection against the effect of external magnetic fields
(B) For guarding the instruments against unauthorized handling
(C) For protection against the effect of moisture in the air
(D) For absorbing heat generated during the functioning of the instrument
98) Why are transformers used in the transmission of electric power?
(A) Because they speed up the transmission
(B) Because they can conserve electrical energy
(C) Because they can reduce transmission losses
(D) Because they help to distribute electrical energy efficiently
99) A mixture of which of the following gases is used in the manufacture of electric bulbs?
(A) Nitrogen and Argon
(B) Nitrogen and Oxygen
(C) Oxygen and Argon
(D) Oxygen and Hydrogen
100) A fresh egg sinks in pure water, whereas it floats in saturated salty water. This is due to
(A) Higher density of the salty water
(B) Higher density of the pure water
(C) The fluid matter inside the egg-shell
(D) The fact that the egg-shell is made of calcium which is heavier than pure water