conserve - Conservation of Energy Thermodynamics Total...

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Conservation of Energy Thermodynamics Total Mechanical Energy Examples Thermodynamics Conservation of energy actually grows out of two main ideas in physics… the First and Second Laws of Thermodynamics. 1. “Energy can not be created or destroyed, only changed from one form to another.” This just basically means the if one thing loses energy, something else must be gaining energy. The opposite is also true. In an ideal situation this transfer of energy would be perfect and complete, but when was the last time you remember our universe being perfect…? This leads us to the second idea… 2. “In any energy conversion, there will always be some waste energy released as heat into the surrounding environment.” Because it is impossible to perfectly transfer energy from one form to another in the real universe, does that mean we are breaking the first law? No, in fact we recognize that the total energy can still be accounted for, it’s just that some of the energy is released as unusable heat. A large branch of physics called Thermodynamics studies the limits of just how close to perfect any device could be in transferring energy. There is a lot more to the laws of thermodynamics , but what you’ve just read are the basics that you need to know. Here’s an example of the two laws happening at the same time… According to the First Law , there is energy being changed from one form to another, battery to motor to kinetic energy. At each step there is some energy being “lost” as waste heat, like the Second Law predicts. This does not mean energy was destroyed. At each step we showed the waste energy being released. If we take that into account, the total energy is the same throughout! The system started with 1000 J of total energy. As you changed energy to other forms you “lost” a total of 200 J to the environment, but still had 800 J at the end… a total of 1000 J still! We are still obeying the First Law . 10/21/2005 © Page 1 of 7
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In most of the stuff we study, we will assume that we are living in a “perfect” universe. This means that for the most part we will obey the
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This note was uploaded on 02/29/2012 for the course PHYS 227 taught by Professor Rabe during the Fall '08 term at Rutgers.

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conserve - Conservation of Energy Thermodynamics Total...

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