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Assertion: Any process taking place in the atmosphere is considered as an isobaric process.

Reason: Work done by the system in that case is p0ΔV. Where, p0 is atmospheric pressure.

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Important Questions on The First Law of Thermodynamics

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JEE Main
IMPORTANT

Assertion: During melting of ice work done by surrounding on (ice + water) system is positive.

Reason: Volume of the given system decreases on melting of ice.

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JEE Main
IMPORTANT

Assertion: Molar heat capacity cannot be defined for an isothermal process.

Reason: In isothermal process pV versus T graph is a dot.

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Assertion: If the initial and the final volumes are equal, then work done by the gas is zero.

Reason In an isochoric process the initial and the final volumes are equal and work done by gas is zero.

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JEE Main
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Assertion: In adiabatic expansion the product of p and V always decreases.

Reason: In adiabatic expansion process, work is done by the gas at the cost of internal energy of gas.

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JEE Main
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Assertion: In isobaric process QΔU is equal to γ=CpCV of the gas.

Reason: For monoatomic gas ratio QΔU in the isobaric process is equal to 53.

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A thermodynamic system is taken from an initial state with internal energy Ui=100 J to the final state f along two different paths iaf and ibf as schematically shown in the figure. The work done by the system along the paths af ,ib and bf are Waf=200 J,Wib=50 J and Wbf=100 J respectively. The heat supplied to the system along the path iaf, ib and bf are Qiaf, Qib and Qbf respectively. If the internal energy of the system in the state b is Ub=200 J and Qiaf =500 J, then the ratio QbfQib is

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One mole of diatomic ideal gas undergoes a cyclic process ABC as shown in figure. The process BC is adiabatic. The temperature at A, B and C are 400 K, 800 K and 600 K respectively. Choose the correct statement.

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MEDIUM
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A Carnot engine operating between temperatures T1 and T2 has efficiency 0.2 . When T2 is reduced by 50 K, its efficiency increases to 0.4. Then, T1 and T2 respectively are