Question

Explain why (a) Two bodies at different temperatures T₁and T₂ if brought in thermal contact do not necessarily settle to the mean temperature (T₁ + T₂ )/2. (b) The coolant in a chemical or a nuclear plant (i.e., the liquid used to prevent the different parts of a plant from getting too hot) should have high specific heat. (c) Air pressure in a car tyre increases during driving. (d) The climate of a harbour town is more temperate than that of a town in a desert at the same latitude.

Answer 1

(a)

Heat flows from higher temperature to lower temperature, if two bodies are at temperature T 1 and T 2 , then heat will continue to flow from a higher temperature body to lower temperature body. It will continue to flow till thermal equilibrium is not maintained, but it will not necessarily be able to reach temperature ( T 1 + T 2 2 ) as the thermal capacities of both the bodies should be equal.

(b)

The necessary property of the coolant is that it should be able to absorb heat at high rate from the different parts of the plant. For this, specific heat of the coolant must be high. Higher the heat capacity, higher will be the heat-absorbing capacity of the coolant.

(c)

The temperature of the air molecules inside the tyre increases when the car is in motion. According to Charles’ Law, temperature is directly proportional to pressure. Therefore, if temperature increases inside the tyre, pressure also increases.

(d)

As the relative humidity in Harbour town is more than that of the desert, therefore the temperature of Harbour town will be more.