GK-Physics Question and Answer
GK-Physics Question and Answer
31. On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because
- mercury is a metal
- density of mercury is greater than that of water
- cohesion of mercury is greater than its adhesion with glass
- cohesion of water is greater than its adhesion with glass
32. Suitable impurities are added to a semiconductor depending on its use. This is done in order to
- increase its life
- enable it to withstand higher voltages
- increase its electrical conductivity
- increase its electrical resistivity
33. Stars twinkle because
- the intensity of light emitted by them changes with time
- the distance of the stars from the earth changes with time
- the refractive index of the different layers of the earth's atmosphere changes
- continuously, consequently the position of the image of a start changes with time
34. It takes much longer to cook food in the hills than in the plains, because
- in the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than 100oC causing an increase in cooking time
- due to low atmospheric pressure on the hills, the water boils at a temperature higher than 100oC and therefore water takes longer to boil
- in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere
- in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking
36. Of the following natural phenomena, tell which one known in Sanskrit as 'deer's thirst'?
- Rainbow
- Earthshine
- Halo
- Mirage
37. Inside an aeroplane, flying at a high altitude,
- the pressure is the same as that outside
- normal atmospheric pressure is maintained by the use of air pumps
- the pressure inside is less than the pressure outside
- normal humidity and partial vacuum are maintained
38. Sound travels with a different speed in media. In what order does the velocity of sound increase in these media?
- Water, iron and air
- Iron, air and water
- Air, water and iron
- Iron, water and air