**Birth of Entropy**

Entropy is the degree of randomness of a thermodynamic system.

In this article we will discuss how the concept of Entropy is originated in thermodynamics.

Let’s consider a reversible heat engine.

From the absolute thermodynamic scale of temperature, we know that.

Q_{1}/Q_{2} = T_{1}/T_{2}

Q_{1}/T_{1} – Q_{2}/T_{2} = 0

Q_{1}/T_{1} + (-Q_{2})/T_{2} = 0

Σ_{CYCLE} (Q/T) = 0

In terms of cyclic integral we can write above equation as

∫_{CYCLE} (∂Q_{R}/T) = 0

We all know that cyclic integral of only a property is zero.

It means ∂Q_{R}/T represents a property. Let’s say it dS.

dS = ∂Q_{R}/T

Integrating both sides

ΔS = ∫(∂Q_{R}/T)

S_{2} – S_{1} = ∫(∂Q_{R}/T)

We declare this point function ‘S’ as entropy.

**Also read:**

*What is efficiency of a heat engine?*