Quantum Mechanics Series- 3 : What is Thermodynamics

Quantum Mechanics 3

What is Thermodynamics ?

The word means the movement of heat, which always flows from a body of higher temperature to a body of lower temperature, until the temperatures of the two bodies are the same. This is called thermal equilibrium.

Heat is correctly described as a form vibration…

The First Law of Thermodynamics

Steam Engines

James Watt (1736 – 1819), A Scot , who had built a working steam engine in 19th century.

Soon after, the son of a Manchester brewer, James Prescott Joule (1818−19), showed that a quantity of heat can be equated to a certain amount of mechanical work.

Then somebody said…. “since heat can be converted into work, it must be a form of energy” (the Greek word energy means “containing work”) But it wasn’t until 1847 that a respectable academic scientist, Hermann von Helmholtz (1821-94), stated…..

Helmholtz

WHENEVER A CERTAIN AMOUNT OF ENERGY DISAPPEARS IN ONE PLACE, AN EQUIVALENT AMOUNT MUST APPEAR ELSEWHERE IN THE SAME SYSTEM.

This is called the law of the conservation of energy.  It remains a foundation of modern physics, unaffected by modern theories.

Rudolf Clausius: Two Laws

In 1850, the German physicist Rudolf Clausius (1822-88) published a paper in which he called the energy conservation law The First Law of Thermodynamics. At the same time, he argued that there was a second principle of thermodynamics in which there is always some degradation of the total energy in the system, some non-useful heat in a thermodynamic process.

Clausius introduced a new concept called entropy – defined in terms of the heat transferred from one body to another.

Entropy is measurement of disorderness of any system. The entropy of an isolated system always increases, reaching a maximum at thermal equilibrium, i.e. when all bodies in the system are at the same temperature.