In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms.After it has been transferred, energy is always designated according to its nature. energy. The capacity or power to do work, such as the capacity to move an object (of a given mass) by the application of force. Energy can exist in a variety of forms, such as electrical, mechanical, chemical, thermal, or nuclear, and can be transformed from one form to another. Energy exists in many different forms. Examples of these are: light energy, heat energy, mechanical energy, gravitational energy, electrical energy, sound energy, chemical energy, nuclear or atomic energy and so on. Kinetic energy is the energy in moving objects or mass. Different types of generators are used to create energy. Electrical energy is caused by moving electric charges called electrons.In power stations, turbines are turned using energy from sources such as heat, wind and moving water. Generators are machines for converting motion energy into electricity.