Energy is the capacity to work. It may exist in many forms. Sun gives its energy in the form of heat and light. Cars are energized by gasoline, a type of chemical stored energy.

Food stored energy enable us to walk around and play. Energy can be found in mechanical, thermal, chemical, electrical, radial (light) and nuclear forms.

   Mechanical Energy       

Mechanical energy is divided to:

 Stored energy (Potential energy)

 Moving energy (kinetic energy)

A lifted object to a certain height stores energy in a potential form. When we leave its holding, it consumes its energy in a moving (kinetic) form. As it is obvious, higher lifts result of further falls.

    Energy units              

Thermal energy is measured in English unit BTU.

One BTU is the amount of energy to raise on Pound of water to one degree Fahrenheit it higher.

One average candy bar contains about one thousand BTU.

Energy can change its form but there is no creation or destroying form of energy. Energy must be remained in one of known forms.

For instance, chemical energy of a battery transformed to electrical energy which then can be changed to light energy in a flashlight.


   Heat Energy       

Heat energy is transferred in three forms:

1-     Conduction

2-     Convection

3-     Radiation