Transformation of Energy
Energy cannot be created, or destroyed; it is merely converted from one form to another. Mechanical energy can be changed by friction into heat energy. The energy of explosives is chemical, as is muscular energy, which is derived from the oxidation, or burning, of foods consumed. Light and radiation represent energy of motion without transport of matter.
Each of these kinds of energy can be converted into any one of others. When a generator produces voltage and an electric motor uses the current, that flows, as a result of that voltage, to perform work, energy is being transformed from one form to another turning the generator and the energy doing the job at the electric motor is mechanical energy. Of all forms of energy, electrical energy is the most convenient and versatile. It can be transmitted to great distances over wires, or sent through the air, as magnetic waves, and converted to electric signals, or impulses at terminal. It can be precisely controlled, from the smallest amounts, up to enormous quantities. It can be changed efficiently into any other form of energy.
All of these forms of energy fall into one of three categories: internal, potential, or kinetic. These categories describe the source of the energy, whether it is from an internal condition, the position of an object, or movement.
Internal Energy
Internal energy is a result of the interaction of molecules in a body or system, and it is independent of any potential or kinetic energy that body may have. Explosives conceal a great deal of internal energy, which does a great deal of work when it is released. Gasoline, coal, wood, and all other combustibles are storehouses of internal energy. When they are burned, energy in the form of heat is released. If the combustible is burned under a boiler, the heat produced generates steam, which in turn may drive a steam engine, and thus the internal energy in the combustible has been expended in useful work.
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