ANYTHING THAT HAPPENS- from a pin drop to an explosion-requires energy. Energy is the capacity for "doing work" (making something happen). Various forms of energy exists including light, heat, sound, electrical, chemical, nuclear, kinetic and potential energies. The law of conservation of energy states that the total amount of energy in the universe is fixed- energy cannot be created or destroyed. In means the energy can only change from one form to another ( energy transfer). For example, potential energy is the energy that "stored" , and can be used in the future. An object gains potential energy when it is lifted; as the objected is released, potential energy changes into the energy of motion (kinetic energy). during transference, some of the energy converted into heat. A combined heat and power station can put some of the otherwise "waste" heat to useful effects in local schools and housing. Most of the Earth's energy is provided by the sun, in the form of electromagnetic radiation. Some of this energy transfers to plant and animal life, and ultimately to fossil fuels, where it is stored in chemical form. Our bodies obtain energy from food we eat, while energy needed for other tasks also, such as heating and transport, can be obtained by burning fossil fuels-or by harnessing natural forces like wind or moving water- to generate electricity. Another source is nuclear power, where energy is released by reactions in the nucleus of an atom. All energy is measured by the international unit, the joule ( J ) . As a guide, one joule is about equal to the amount of energy needed to lift an apple one metre.
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