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Check my understanding of electrical energy please.

  1. Aug 19, 2009 #1
    When work is done on a Coulomb of charge, it gains potential energy equal to the amount of work done on it. Now, since this charge is moving, it's electric field is changing. Because of that, a changing magnetic field surrounds a charge. Now, since this only happens when the Coulomb is moved by a voltage, the PE of the charge will be in the form of an electromagnetic field. This energy does work on devices when the fields set up voltage drops across them.

    Any issues here?
  2. jcsd
  3. Aug 20, 2009 #2
    Simplified: My assumption is that electrical potential energy is in the form of EM or electric fields.
  4. Aug 20, 2009 #3
    Wow, tough crowd. I guess I make really confusing topics.
  5. Aug 20, 2009 #4


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    Staff: Mentor

    LOL. Well, at least for me, I didn't respond because you were neglecting frequency and resonance effects, which have a big influence on what happens with moving charges and EM radiation energy propagating away.

    If you slowly move charge, you will get a change in energy that corresponds to the traditional DC energy equations (like energy stored on a cap). If you quickly move charges (with respect to the size of the conductors that you are moving them along), then you will get some EM losses.

    Could you please be more specific about your question? Geometry, frequeency, etc.? Thanks.
  6. Aug 20, 2009 #5


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    Science Advisor
    Homework Helper

    Hi user111_23! :smile:

    (btw, it's "coulomb", with a small "c", same as any other unit :wink:)
    PE is another name for work done by a conservative force.

    A magnetic field surrounds a charge only if the charge is moving (relative to a particular observer).

    The PE of the charge is the result of having moved through an external field.

    What does the field of the charge itself have to do with it? And how can PE (a scalar) be "in the form of a field"? :confused:
  7. Aug 21, 2009 #6
    I'm sort of a physics newb so bear with me. :tongue:

    I learned that electrical energy is in the form of EM waves/fields. So I'm trying to see whether the PE supplied to a charge through voltage is also electromagnetic energy. Weird question, I know.
  8. Aug 21, 2009 #7
    yea that's what I'm thinking too, to me, PE and the EM fields of a charge is unrelated

    user111_23 perhaps you could clarify the question a bit or give more detail on your hypothesis
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