1.

Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas ? (Assume non-expansion work is zero) (1) Adiabatic process : ΔU = –w (2) Cyclic process : q = – w (3) Isothermal process : q = – w (4) Isochoric process : ΔU = q

Answer»

Correct option (1) Adiabatic process : ΔU = –w

Explanation:

Ist law of thermodynamics 

ΔE = q + w

1. Adiabatic process 

q = 0, (ΔE = w) or (ΔU = w) 

2. Cyclic process 

ΔE = 0, (q = – w) 

3. Isothermal process 

ΔE = nCVΔT, (ΔT = 0) 

ΔE = 0, (q = –w) 

4. Isochoric process ΔV = 0 

w = PΔV = 0 

ΔE = q



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