Question

What is the principle of increase of entropy?

Answer 1

Hint:To solve this question, we are going to firstly define the entropy of a system then, the principle of entropy is defined after which the inequality and equality relations for the entropy are given along with their specification with the reversible or irreversible nature of the process of system.

Formula used: The entropy change of a system is given by the equation:
\[\Delta S = \dfrac{{dQ}}{T}\]
Where, \[dQ\]is the change of heat of the system and \[T\]is the temperature of the system.

Complete step-by-step solution:
Entropy is defined as the property of the randomness or disorder in a system. The principle of increase of entropy states that the entropy of the Universe also increases. It never decreases but remains constant only in a reversible process. For an isolated system:
\[\Delta S > 0\], for irreversible processes
\[\Delta S = 0\], for reversible processes
\[\Delta S < 0\], this is an impossible case
The entropy change of a system is given by the equation:
\[\Delta S = \dfrac{{dQ}}{T}\]
Where, \[dQ\]is the change of heat of the system and \[T\]is the temperature of the system.
Therefore, the entropy of an isolated system either increases or in the limit, remains constant.

Note:It is to be noted that the entropy is always greater than the change of heat of system per unit degree of temperature for an irreversible process while the entropy is always equal to the change of heat of system per unit degree of temperature for a reversible process. It is never less than the change of heat of a system per unit degree of temperature.