Energy is the capacity to do work. Any form of energy can be transformed into another form. Energy has been expressed in several different units such as ergs and calories. At present, the accepted unit of measurement for energy is the SI unit of energy, the joule.
In all such energy transformation processes, the total energy remains the same. Energy may not be created nor destroyed, even if when transformed into thermal energy.
There is a definite relationship between mechanical work done W and heat produce H, i.e.
W=JH
Where J is known as Joule Mechanical equivalent of heat, which is equal to 4.184X107 ergs and which is equal to 4.184 joules.
Work
When work is done by a thermodynamic system, it is usually a gas that is doing the work. The amount of mechanical work done can be determined by an equation derived from Newtonian mechanics
Work = Force x Distance moved in the direction of the force
It can also be described as the product of the applied pressure and the displaced volume:
Work = Applied pressure x Displaced volume
The unit of work is joule, J, which is defined as the amount of work done when a force of 1 Newton acts for a distance of 1 m in the direction of the force.
1 J = 1 Nm
Sources of Energy
Sun and stars are considered as the prime source of energy. The sunlight we receive gives us heat and light. This energy is then converted into other forms of energy by use of various technical means.
Also the role of stars is appreciable as they are responsible for nuclear fusion reactions which has provided us Hydrogen and other elements which are formed from hydrogen.
