A Carnot engine operates with source at 127°C and sink a

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 Multiple Choice QuestionsMultiple Choice Questions

131.

One mole of a monoatomic ideal gas undergoes the process A → B in the given p-V diagram. The molar heat capacity for this process is

          

  • 3R2

  • 13 R6

  • 5 R2

  • 2R


132.

A lead bullet penetrates into a solid object and melts. Assuming that 50% of its kinetic energy was used to heat it, the initial speed of the bullet is (the initial temperature of the bullet is 25oC and its melting point is 300°C). Latent heat of fusion of lead= 2.5 x 104 J/kg and specific heat capacity of lead= 125 J/kg-K

  • 100 m/s

  • ≈ 490 m/s

  • 520 m/s

  • 360 m/s


133.

The slope of isothermal and adiabatic curves are related as

  • isothermal curve slope= adiabatic curve slope

  • isothermal curve slope = γ × adiabatic curve slope

  • adiabatic curve slope = γ× isothermal curve slope

  • adiabatic curve slope =12× isothermal curve slope


134.

The volume of an ideal gas is doubled in an isothermal process. Then, which of the following is true?

  • Work done by the gas is positive

  • Work done by the gas is negative

  • Internal energy of the system decreases

  • Internal energy of the system increases


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135.

When an ideal monoatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is

  • 2 / 5

  • 3 / 5

  • 3 / 7

  • 5 / 7


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136.

A Carnot engine operates with source at 127°C and sink at 27°C. If the source supplies 40 kJ of heat energy, the work done by the engine is

  • 30 kJ

  • 10 kJ

  • 4 kJ

  • 1 kJ


B.

10 kJ

Efficiency, η = 1 - T2T1

              η = 1 - 273 + 27273 + 127

              η  = 1 - 300400 

                   = 1 -34

              η  = 14

Also, The efficiency defination given by

        η  = Work done by engineHeat supplied by source

             = W40 kJ

∴   W = 40 η 

           = 40 × 14

     W = 10 kJ   


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137.

Assertion:  The specific heat of a gas in an adiabatic process is zero and in an isothermal process is infinite.

Reason:  Specific heat of gas is directly proportional to change of heat in system and inversely proportional to change in temperature.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


138.

A thermodynamic process is carried out from an original state D to an intermediate state E by the linear process shown in figure

The total work is done by the gas from D to E to F is

  • 100 J

  • 800 J

  • 300 J

  • 250 J


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139.

Assertion:  In an isolated system the entropy increases. 

Reason:  The process in an isolated system is adiabatic only.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


140.

3 mole of hydrogen is mixed with 1 mole of neon. The molar specific heat at constant pressure is

  • 9 R4

  • 9 R2

  • 13 R4

  • 13 R2


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