Heat and Thermodynamics

8.1 Principle of Conservation of Energy

It states that the sum total of the energy of the universe is an invariant; it can only transform into different forms. This principle forms the fundamental postulate in Physics. Regarding the forms of energy, we have the following categories:

1. The mechanical energy, which may be kinetic or potential corresponding to mechanical work which is measured by mechanical force × displacement.
2. The non-mechanical energy such as heat, light, electrical and magnetic energies.

In thermodynamics, we deal only with the relation between two forms of energy—heat and mechanical work. The quantitative law of transformation of mechanical work into heat is given by the Joule's law

 

W = J × Q

 

where W is the amount of mechanical ...