Temperature in the freezer of a refrigerator is being maintained at -13^o C and room temperature on a particular day was 42^o C. Calculate the coefficient of performance of the refrigerator.

Why a gas is cooled when it expand?

Two isothermal curves do not intersect each other, why?

Why air quickly leaking out of a balloon becomes cooler?

A room can be cooled by opening the door of a refrigerator.Is it true or false?

What are the forces which make any process irreversible?

The coefficient of performance of a refrigerator depends on which factors?

Find the efficiency of the Carnot engine working between boiling point and freezing point of water.

Which thermodynamic law put restrictions on the complete conversion of heat into work?

What type of process is a Carnot cycle?

A person of mass 60 kg wants to lose 5 kg by going up and down a 10 m high stairs. Assume he burns twice as much fat while going up than coming down. If 1kg of fat is burnt on expending 7000 kcal calories, how many times must he go up and down to reduce his weight by 5 kg?

A cylinder with a movable piston contains 3 moles of hydrogen at standard temperature and pressure. The walls of the cylinder are made of a heat insulator, and the piston is insulated by having a pile of sand on it. By what factor does the pressure of the gas increase if the gas is compressed to half its original volume ?

A refrigerator is to maintain estables kept inside at 9⁰C. If the room temperature is 36⁰C. Calculate the coefficient of performance.

In a refrigerator, one removes heat from a lower temperature and deposits to the surroundings at a higher temperature. In this process, mechanical work has to be done, which is provided by an electric motor. If the motor is of 1kW power and heat is transferred from -3°C to 27°C. Find the heat taken out of the refrigerator per second assuming its efficiency is 50% of a perfect engine.

A steam engine delivers 5.4 x 10⁸ J of work per minute and services 3.6 x 10⁹ J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?

Calculate the work done for adiabatic expansion of a gas.

A Carnot engine absorbs 6 x 10⁵ cal at 227 ^o C. Calculate work done per cycle by the engine if its sink is maintained at 127^o C.

Explain, why?
(i) 500 J of work is done on a gas to reduce its volume by compression adiabatically. What is the change in internal energy of the gas?
(ii) 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.
(iii) The climate of a harbour town is more temperate than that of a town in a desert at the same latitude

What is a heat engine? What is the best way to increase efficiency of a heat engine? Is it possible to design a thermal engine that has 100% efficiency?

An ideal refrigerator is working between the temperature of ice and temperature of atmosphere at 300 K. Find the energy which has been supplied to it to freeze 2 kg of water at 0^o C. Given that latent heat of ice 3.33 x 10⁵ J/Kg.