81.
A small gap is left at the joints of rails in a railway track to

82.
Pipelines in cold countries often burst in winter, because

83.
In severe winter, in cold countries water pipes burst because

84.
Railway tracks are banked on curves so that

85.
The density of the liquid when heated

86.
Thermocouple consists of

87.
Water has maximum density at

88.
When water freezes its density

89.
Which of the following are methods of heat transfer?

90.
Heat energy is transferred by conduction whenever molecules