Which of the processes described below are irreversible ?

Options

A. The increase in temperature of an iron rod by hammering it
B. A gas in a small container 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

Explanation

(a) When the rod is hammered, the external work is done on the rod which increases its temperature. The process cannot be retracted itself.
(b) In this process energy in the form of heat is transferred to the gas in the small container by big reservoir at temperature `T_(2)`.
(d) As the weight is added to the cylinder arrangement in the form of external pressure hence, it cannot be reversed back itself.