question_answer 17)

                  Which of the processes described below are irreversible?                 (a) The increase in temperature of an iron rod by hammering it.                 (b) A gas in a small cantainer at a temperature \[{{T}_{1}}\] is brought in contact with a big reservoir at a higher temperature \[{{T}_{2}}\] which increases the temperature of the gas.                 (c) A quasi-static isothermal expansion of an ideal gas in cylinder fitted with a frictionless piston.                 (d) An ideal gas is enclosed in a piston cylinder arrangement with adiabatic walls. A weight W is added to the piston, resulting in compression of gas.                

Answer:

                  (a, b, d) In irreversible process, original state of system cannot be regained.