حفظ الطاقة Conservation Energy
Law of Conservation
|We have often heard phrases like, "Conserve energy; turn off the lights." To scientists, conservation of energy is something entirely different. The law of conservation of energy states that the total amount of energy in a system remains constant ("is conserved"), although energy within the system can be changed from one form to another or transferred from one object to another.
Energy cannot be created or destroyed, but it can be transformed. That's really what we mean when we say we are "using" energy. The law of conservation of energy means that when energy is being used, it is not being used up. Instead, it is being changed from one form into another. A car engine burns fuel, converting the fuel's chemical energy into mechanical energy to make the car move. Windmills change the wind's energy into mechanical energy to turn turbines, which then produce electricity. Solar cells change sunlight (radiant energy) into electrical energy
Energy may change form many times on its way to doing work in your home, such as toasting bread. In the process, some energy is converted into unwanted thermal energy or waste heat. In fact, it is impossible to convert one form of energy into another without wasting some energy.
In many energy conversions, more energy is wasted than is used for work. For example, automobile engines typically waste more than two-thirds of the total energy used, primarily through heat.
On the other hand, electrical motors convert electrical energy into mechanical energy with only about 10 percent of the energy wasted via heat. Energy efficiency means converting energy from one form to another with the least possible
waste.law of nature is called the law of conservation of energy.
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