Question

The second law of thermodynamics can be given as __________.

Answer 1

The second law of thermodynamics:

1. The entropy of the universe increases as a result of any spontaneous process.
2. This law states that the entropy of an isolated system will never decrease over time.
3. It explains that converting heat energy to mechanical energy with 100% efficiency is impossible.
4. Mathematically it can be stated as, $∆S_{univ}>0$, here $∆S_{univ}$ change in entropy of the universe.
5. There are two statements for the second law of thermodynamics,

Kelvin-Planck Statement- It is impossible for a heat engine to produce a net amount of work in a complete cycle if it exchanges heat only with bodies at a single fixed temperature.

The Clausius statement: It is impossible to construct a device that operates on a cycle and produces no other effect than the transfer of heat from a cooler body to a hotter body.

1. Change in entropy can be calculated by, $dS=\frac{dQ}{T}$.

$dS$ is the change in entropy,

$dQ$ is the change in heat energy,

$T$ is the Temperature.