SL: Heat and Directionality vs Reversibility

Heat and Directionality vs Reversibility

Few caveats about directionality:

Note:

Reversible processes do not exhibit directionality (consider the piston-cylinder with small and large weights).

Definition:

Second Law: No process is possible which consists solely in the transfer of heat from one temperature level to a higher one.

Definition:

Second Law: It is impossible for a cyclic process to convert the heat absorbed by a system completely into work done by the system.

Definition:

The second law states that for any irreversible (real) process the entropy of the universe increases, while for any reversible process the entropy of the universe remains unchanged.

Definition:

$\Delta s_{univ} \ge 0$