$Assertion :$ In an isolated system,the entropy increases.
$Reason :$ The processes in an isolated system are adiabatic.

$A$ solid body of constant heat capacity $1\,J/^{\circ}C$ is being heated by keeping it in contact with reservoirs in two ways:
$(i)$ Sequentially keeping in contact with $2$ reservoirs such that each reservoir supplies the same amount of heat.
$(ii)$ Sequentially keeping in contact with $8$ reservoirs such that each reservoir supplies the same amount of heat.
In both cases, the body is brought from an initial temperature $100^{\circ}C$ to a final temperature $200^{\circ}C$. The entropy change of the body in the two cases respectively is:

During phase change,entropy

Which limitation of a heat engine is imposed by the second law of thermodynamics?

The entropy of a thermodynamic system does not change when this system is used for:

Why is a heat engine never $100\%$ efficient?