Which of the processes described below are irreversible ?

1.	Which of the processes described below are irreversible ?
Answer» The increase in temperature of an iron rod by hammering it. 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. A quasi-static isothermal expansion of an ideal gas in cylinder fitted with a frictionless piston. 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. Solution :(A) During hammering the rod external work is done on the rod in hammering and raises the temperature, so process is not reversible. B) The heat of bigger container transfer to smaller container at temperature `T_2` to `T_1` the process cannot be retraced itself. (C) A quasi-static isothermal EXPENSION of an ideal gas in cylinder fitted with a frictionless pistion. (D) As the weight is added to the cylinder arrangement in the form of external pressure HENCE, it cannot be reversed back itself.

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