Physics Classes

Tag: thermodynamics

  • 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.

  • Important questions of thermodynamics

    Important questions of thermodynamics

    Important questions of thermodynamics

    This assignment contains all important questions of thermodynamics. It will help the students of class 11th to practice the entire chapter of thermodynamics for the final examination of class 11th , in cbse/icsc and   all state board examinations.

    IMPORTANT QUESTIONS  OF THERMODYNAMICS

    1. During an adiabatic process, the pressure of a gas is found to be proportional to cube of its absolute temperature what is the ratio of Cp/Cv ?
    2. Can a room be cooled by opening the door of a refrigerator in a closed room?
    3. Which molecules ice at 0⁰C or water at 0⁰C have greater potential energy and why?
    4. (a) can the temperature of system be increases without heating it? (b) can heat be added to a system without increasing its temperature?
    5. A refrigerator, whose coefficient of performance β is 5 extract heat from the cooling compartment at the rate of 250 j per cycle.
    • (a)How much work per cycle is required to operate the refrigerator cycle? (b) how much heat per cycle is discharged to the room which acts as high temperature reservoir?
    1. A piston divides a closed gas cylinder gas into two parts. Initially the piston is kept pressed such that one part has a pressure p and volume 5V and the other part has pressure 8p and volume v; the piston is now left free. Find the new pressure and volume for the isothermal and adiabatic prosses.
    2. Two car not engine A and B ate operated in series. The first one A receive heat at 800k and rejects to a reservoir at TK. The second engine B receives the heat rejected by the first engine and in turn
    3. A mass of diatomic gas (=1.4) at a pressure of 2 atmosphere is compressed adiabatically, so that its temperature rises from 27⁰C to 927⁰. What is the pressure of the gas in the final state.
    4. State and explain the isothermal process, derive the expression for work done in isothermal process.
    5. State and explain the adiabatic process, derive the expression for work done in adiabatic process.

     

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