charging - Charging by Friction, Induction, & Conduction...

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Charging by Friction The only reason that we are able to use electricity in our modern world is that it is possible to separate positive and negative charges from each other. One way to do this is by rubbing two different materials together, a process known as charging by friction . Since the two objects are made of different materials, their atoms will hold onto their electrons with different strengths. As they pass over each other the electrons with weaker bonds are “ripped” off of that material and collect on the other material. Example 1 : Rub a piece of ebonite (very hard, black rubber) across a piece of animal fur . Explain what happens. The fur does not hold on to its electrons as strongly as the ebonite . At least some of the electrons will be ripped off of the fur and stay on the ebonite . Now the fur has a slightly positive charge (it lost some electrons) and the ebonite is slightly negative (it gained some electrons).The net charge is still zero between the two… remember the conservation of charge. No charges have been created or destroyed, just moved around. Example 2 : Rub a glass rod with a piece of silk . Explain what happens. This is the same sort of situation as the one above. In this case the silk holds onto the electrons more strongly than the glass . Electrons are ripped off of the glass and go on to the silk . The glass is now positive and the silk is negative . You may be wondering how you could ever keep track of this, since the combinations of different materials being rubbed on each other is infinite. Rather than try to keep track off all the combinations, we can arrange some of the more common possibilities in a chart called an “ Electrostatic Series ” that lets you find out which material will be positive and which one will be negative. An electrostatic series in arranged in terms of the relative “hold” that different materials have on their electrons. sulphur
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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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charging - Charging by Friction, Induction, & Conduction...

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