From a practical perspective, we have:
The concept of energy transformation can be illustrated in a number of common activities. An engine, such as the engine in a car, converts the chemical energy of gas and oxygen into the mechanical energy of engine movement. A light bulb changes the chemical energy of the bulb into electromagnetic radiation, or light. Windmills harness the energy of the wind and convert it into mechanical energy in the movement of the turbine blades, which is then converted to electrical energy. Solar panels transform light to electricity.