Categories

# Very important questions of thermodynamics

Important questions of thermodynamics-

1. What is the zeroth law of thermodynamics ? How does it lead us to the concept of temperature?

2. Define isothermal and adiabatic process . What are the conditions necessary for such process to occur?

3. State and explain the first law of thermodynamics. Also write its limitations.

4. Define two principle specific heat of gas . Why is Cp greater then Cv ?

5. Define two specific heat of a gas and show that the difference between them is constant . (or, Derive Mayer’s formula).

6. Describe melting and boiling process on the basis of first law of thermodynamics.

7. Show that for an adiabatic change in a perfect gas PVƳ=constant, where P is pressure and V is the volume and Ƴ is the ratio of two specific heat of the gas.

8. Define isothermal change . Calculate the amount of work done when perfect gas expand isothermally.

9. Define adiabatic change . Calculate the amount of work done when perfect expands adiabatically.

10.  Derive a relation between the slopes of an isothermal and adiabatic curve.

11. State second law of thermodynamics in the two usual forms. Show that both these forms are equivalent to each other. Also write the limitations of second law of thermodynamics.

12. What is the heat engine ? Explain the basic principle with the help of a flow diagram. Also explain its efficiency .

13. What is a Carnot cycle? Find its efficiency. Does this efficiency depends on the working fluid ?Does any actual engine reach to the efficiency of Carnot engine ? Give reason  .

Numericals-

1. A cylinder with a movable piston contains 3 mole of hydrogen at standard temperature and pressure. The wall of the cylinder is made of insulating . By what factor does the pressure of the gas increase if the gas is compressed to half of its initial value?    Ans-21.4

2. In changing the states of a gas adiabatically from an equilibrium states A to another Equilibrium state B , an amount of work equal to 22.3J is done on the system . If the gas is taken from state A to B via process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in latter case ?               Ans-16.9 J

3. A steam engine delivers 5.4×108J of work per minute. What is the efficiency of the engine ? How much heat is wasted per minute?                        Ans- 15%, 3.06x10J .

4. An electric heater supplies heat to a system at a rate of 100W . The system prefer work at the rate of 75J/sec. At what rate the internal energy increasing?                  Ans-25 watt.

5. A thermodynamic system is taken from an original states D to an intermediate state E by the liner process shown in fig,

Its volume is then reduced to the original value From E to F by an isobaric process . Calculate the total work done by the gas from D to E to F.