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Capacitor Analogy

  1. May 2, 2007 #1
    I have read this site by William J Beaty http://amasci.com/emotor/cap1.html
    It lucidly explains the functioning of the capacitor with a water analogy.
    I have a question with respect to this.
    If in a capacitor we introduce a dielectric with dielectric constant k then can a parellel be drawn with respect to this analogy.
  2. jcsd
  3. May 2, 2007 #2
    Yes. You could say that in the analogy, the rigidity of the rubber plate accounts for the capacity: a thicker plate (more rigid) means less capacity and a thinner more capacity. The introducing a dielectric is the same as changing thick rubber plate for a thinner one.
  4. May 2, 2007 #3

    That article is a little iffy. It's not wrong, but neither is the textbook definition. Of course capacitors have no net charge change. This can be seen simply from the sign convention that one plate has charge +Q and the other has charge -Q.

    However, each plate does experience a net charge gain, which can be seen simply by separating a charged capacitor and using a single plate to induce a current flowing to a ground.
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