Air Neslo Beng On Monday, September 20, 2010

          Macroscopic matter is made of atoms and molecules bound together by electrical forces.  The atoms are composed of electrically neutral neutrons, positively charged protons, and negatively charged electrons.  In batteries, and other sources of electrical power, positive and negative charges are separated usually by some mechanical process.  Since unlike charges attract each other, work must be done to separate them.  

           You probably have already studied conservation of (mechanical) work and energy in Newtonian mechanics.  Electrical energy is simply another form of energy, and what we have found is that all kinds of energy can change form, from one kind to another, but the total energy of an independent system is conserved.  Recall that energy cannot be created or destroyed, but changed from one form to another.  Under the right conditions, we can get back the work we put into separating the charges.  A source of electricity is rated by the “voltage”, or work per unit charge which could be recovered if a unit positive charge moved from the “positive” side of the battery or electricity source to the “negative” side.  (or, which is what usually happens, a unit negative charge moved from the “negative” side of the battery to its “positive” side).


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