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Electric charges moving and magnetic field

  1. Mar 6, 2007 #1
    I know that a current creates a magnetic field and so do moving electric charges. My question is how fast a single charge moves so that it will create a magnetic field. Should its velocity be around c to make that?

    Thks
     
  2. jcsd
  3. Mar 6, 2007 #2

    Meir Achuz

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    A moving electron creates a magnetic field B~vXE/c.
     
  4. Mar 6, 2007 #3
    Oh, cool, I can calculate the magnetic field of a current by this formula as well. Thanks.
     
  5. Mar 6, 2007 #4
    This is the magnetic field generated by a moving electric charge.

    [tex]\vec{B} =\frac{q \vec{v} \times \vec{r}}{r^3}[/tex]
     
  6. Mar 7, 2007 #5
    I think that no matter how much of the charge are given, there should have a magnetic made. But whether or not it is easy to found .
    is it ?
     
  7. Mar 7, 2007 #6
    to answer haiha's question, typically in an electrical ckt, the electrons dont move around with speed of light..infact surprisingly it moves with a drift velocity. this is typically around 1cm/sec ! yes, electrons' drift velocity is very slow...it is the velocity of the signal that moves with speeds comparable to light( well it depends upon the dielectric co-effs etc). "signal" here roughly means the electro-magnetic field through space...
     
  8. Mar 7, 2007 #7

    Meir Achuz

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    The magnetic field of a single moving charge is a tricky calculation using Special Relativity, especially if the charge is accelerating.
     
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