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Maxwell's 4th equation

  1. May 30, 2003 #1


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    Hello ppls,
    i am reading my text and came across this interesting equation here.
    my question is is simple lamens terms maxwells 4th equation: displacement current, how does it work in simple terms please. I ask cause ive read the definition and discussion in the book even though its concise im a bitconfused of how it works other than its just a displacement of current.
    Can anyone please explain this principle better.
    Dx :wink:
  2. jcsd
  3. May 30, 2003 #2
    (My Physics book lists that one as the 3rd equation, but it makes no difference on how you number them.)
    This equation is also known as Ampere's Law.
    It basically means that both conduction current and displacement current act as sources of magnetic field.
    Which makes sense since any moving electrons, or current, should be a source of magnetic field as long as it's in the correct (integration-)path.
  4. May 30, 2003 #3
    DX, a magnetic field is just a relativistic part of moving electric field. Thus it is created by changing electric field (say, by moving electric charge, or just as appers to observer moving by stationary charge).

    Magnetic field not a fundamental phyical field, but is just a mathematical result of Lorents transformation of coordinates for electric field from one reference system to another.

    (Knowing this nature of magnetic field helps to understand its properties and its behavior better).
    Last edited by a moderator: May 30, 2003
  5. May 30, 2003 #4


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    Perhaps DX's problem is with the definition, or intuition, of displacement current? When I took EM (decades ago) that was a mystery wrapped up in an enigma; since I have learned the relativistic view of EM it doesn't seem necessary anymore. Can we learn to see it as just something Maxwell, trapped in the pre-relativity view, needed to pretend he thought existed?
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