Thermodynamics

Thermodynamics

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Thermal Physics

Thermal Properties of Matter
Thermodynamics
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  1. A thermodynamic system is taken through the cycle ABCD as shown in figure. Heat rejected by the gas during the cyclic process is :​









  1. View Hint View Answer Discuss in Forum

    ∵ Internal energy is the state function.
    ​∴ ​In cyclie process; ∆U = 0 ​
    According to 1st law of thermodynamics​

    ∆Q = ∆U + W

    So heat absorbed ​
    ∆Q = W = Area under the curve ​
    = –  (2V) (P) = –  2PV ​
    So heat rejected = 2PV

    Correct Option: A

    ∵ Internal energy is the state function.
    ​∴ ​In cyclie process; ∆U = 0 ​
    According to 1st law of thermodynamics​

    ∆Q = ∆U + W

    So heat absorbed ​
    ∆Q = W = Area under the curve ​
    = –  (2V) (P) = –  2PV ​
    So heat rejected = 2PV

  1. In thermodynamic processes which of the following statements is not true?​​








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    ​In an isochoric process volume remains constant whereas pressure remains constant in isobaric process.

    Correct Option: A

    ​In an isochoric process volume remains constant whereas pressure remains constant in isobaric process.

  1. One mole of an ideal gas at an initial temperature of T K does 6R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of gas will be​​








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    T1 = T , W = 6R joules , γ =
    5
    3

    W =
    P1V1 - P2V2
    		 =
    nRT1 - nRT2
    γ - 1γ - 1

    =
    nR(T1 - T2)
    γ - 1

    n = 1 , T1 = T ⇒
    R(T - T2)
    		 = 6R
    (5 / 3) - 1

    ⇒ T2 = ( T–4)K

    Correct Option: A

    T1 = T , W = 6R joules , γ =
    5
    3

    W =
    P1V1 - P2V2
    		 =
    nRT1 - nRT2
    γ - 1γ - 1

    =
    nR(T1 - T2)
    γ - 1

    n = 1 , T1 = T ⇒
    R(T - T2)
    		 = 6R
    (5 / 3) - 1

    ⇒ T2 = ( T–4)K

  1. If Q, E and W denote respectively the heat added, change in internal energy and the work done in a closed cyclic process, then :​








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    In a cyclic process, the initial state coincides with the final state. Hence, the change in internal energy is zero, as it depends only on the initial and final states. But Q & W are non-zero during a cycle process.

    Correct Option: C

    In a cyclic process, the initial state coincides with the final state. Hence, the change in internal energy is zero, as it depends only on the initial and final states. But Q & W are non-zero during a cycle process.

  1. A monoatomic gas at a pressure P, having a volume V expands isothermally to a volume 2V and
    then adiabatically to a volume 16V. The final pressure of the gas is : (take γ =
    5
    		)
    3








  1. View Hint View Answer Discuss in Forum

    For isothermal process P1V1 = P2V2 ​

    ⇒ PV = P2(2V) ⇒ P2 =
    P
    2
    ​
    For adiabatic process
    P2V2γ = P3V3γ
    ⇒
    P
    		(2v)γ = (P316v)γ
    2

    ⇒ P3 =
    3
    1
    		5 / 3 =
    P
    2864

    Correct Option: C

    For isothermal process P1V1 = P2V2 ​

    ⇒ PV = P2(2V) ⇒ P2 =
    P
    2
    ​
    For adiabatic process
    P2V2γ = P3V3γ
    ⇒
    P
    		(2v)γ = (P316v)γ
    2

    ⇒ P3 =
    3
    1
    		5 / 3 =
    P
    2864