Book: HC Verma - Concepts of Physics Part 2
Chapter: 27. Specific Heat Capacities of Gases
Subject: Physics - Class 12th
Q. No. 6 of Short Answer
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Can a process on an ideal gas be both adiabatic and isothermal?
According to the first law of thermodynamics,
dQ = dU + dW = nCvdT + dW … (i),
where
dQ = heat supplied
dU = change in internal energy
dW = work done on the gas
n= number of moles
Cv = specific heat capacity at constant volume
dT = change in temperature
For an adiabatic process, dQ(heat supplied) = 0.
An adiabatic process occurs without the transfer of heat or mass of substances between the thermodynamic system and the surrounding.
For an isothermal process, dT(change in temperature) = 0
An Isothermal process is a change of system, in which the temperature remains constant ∆T=0.
Putting these values in (i), we get
dW = 0,
which is not possible for either of the processes.
dW = 0 only in the case of a process where the volume is constant that is dV = 0,
since dW = PdV,
where P = pressure and dV = change in volume.
Hence, we conclude that a process cannot be both adiabatic and isothermal.
