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Capacitors and Electric Fields

  1. May 17, 2009 #1
    There are no electric fields outside of a charged capacitor as they are cancelled out due to superposition, right?! So why is there a flow of current when a cable is connected to both ends of the capacitor?

    I was told that there might be an E field in the wires. How come? Where does it come from?
     
  2. jcsd
  3. May 17, 2009 #2

    vk6kro

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    A charged capacitor can be discharged by connecting the plates together.
    That is what you do when you connect the two ends of a charged capacitor by a piece of wire.

    A capacitor is made by making layers of metal and dielectric in a spiral on a central rod.
    This means that one of the layers of metal must be on the outside of the capacitor. ie they can't both be on top.
    So, this plate of the capacitor would certainly have a field around it if the capacitor was charged.
    Maybe your first assertion isn't correct for normal capacitors?

    Not sure what you mean by an "E" field. The leads of a capacitor can certainly have a voltage between them. There is a capacitor in all microwave ovens that is very capable of killing you.
     
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