Consider a cycle followed by an engine (figure.) 1 to 2 is isothermal 2 to 3 is adiabatic 3 to 1 is adiabatic Such a process does not exist, because

Question

Consider a cycle followed by an engine (figure.) 1 to 2 is isothermal 2 to 3 is adiabatic 3 to 1 is adiabatic Such a process does not exist, because, heat is completely converted to mechanical energy in such a process, which is not possible, mechanical energy is completely converted to heat in this process, which is not possible, curves representing two adiabatic processes don't intersect, curves representing an adiabatic process and an isothermal process don't intersect

MARKS App · Accepted Answer

(a) As the given process is a cyclic process, which starts from 1 and it returns to the original state 1 . Hence, change in internal energy d U = 0 . So, d Q = d U + d W $ ⇒ ( d Q = d W ) = 0 + d W $ Hence, total energy supplied to system converted to mechanical work done by the gas which is not possible by second law of thermodynamics. (c) When the gas expands adiabatically then the curve from 2 to 3 . It is not possible to return to the same state without heat supplied, hence the process 3 to 1 cannot be adiabatic.

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