61.
In a railway track, two rails are joined end to end with a gap in between them because

62.
Air coolers are more suitable for

63.
We feel cool when we sit near the fan, this is because

64.
When hot-water is sprinkled on a hotter glass tumbler, it breaks because

65.
A gap is left between two rails of a railway track to accommodate...... of the metal.

66.
Which of the following is arranged in order of decreasing conductivity?

68.
Which metal is the best conductor of heat?

69.
When hot liquid is poured into a thick glass tumbler, it cracks because glass :

70.
Mud houses are cooler in summers and warmer in winters as compared to brick houses because