Thermodynamics reasoning

Question 1

Two bodies at different temperatures T1
and T2
if brought in thermal contact do
not necessarily settle to the mean temperature (T1
+ T2 )/2.

Answer 1

In thermal contact, heat flows from the body at higher temperature to the body at lower temperature till temperatures become equal. The final temperature can be the mean temperature (T 1 + T 2)/2 only when thermal capacities of the two bodies are equal.

Question 2

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.

Answer 2

The function of a coolant in a chemical or nuclear plant is to absorb as much heat as possible and prevent rise in temperature of the system. The coolant should have a high specific heat. This is because higher the specific heat of the coolant, higher is its heat-absorbing capacity and vice versa.

Question 3

Air pressure in a car tyre increases during driving

Answer 3

Frictional force acts between the tyres of the car and the road. During driving, the work is done against the frictional force which is converted into heat. Therefore, the temperature increases while the volume of the tyre remains constant. Now as per the Charles law, P α T hence, pressure of gas in the tyre increases.

Question 4

The climate of a harbour town is more temperate than that of a town in a desert
at the same latitude.

Answer 4

The humidity in harbour town is generally much greater than humidity in a desert. Since humidity is a measure of water vapor content in the atmosphere and the specific heat of water vapor is very high
the temperature fluctuations in harbour towns are generally lower than those in desert regions. Hence, the climate in harbour towns is more temperate than that of town in a desert at the same latitude.