Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Moving charges and varying magnetic fields

  1. Feb 18, 2017 #1
    I understand that a steady flow of current will not induce currents in near by conductors. But, what about a steady flow of current that is being accelerated perpendicularly by a uniform magnetic field? Wouldn't this current produce a time varying magnetic field?
    This is a conductive disk with axial current flow.
    As the current is curved to the right, shouldn't it emit radiation in the direction of the blue lines?
  2. jcsd
  3. Feb 19, 2017 #2
    Nobody has answered yet here, so I'll just give my best guess of saying: yes, I agree, these charges are being accelerated, and thus should emit radiation.

    Do you have reason to believe it is not the case?
  4. Feb 19, 2017 #3
    Well because radiation can only be varying. So; if it does emit radiation, it would mean dc to ac conversions could be done with just a copper disk and a magnet.
  5. Feb 20, 2017 #4
    What do you mean by "steady" and "accelerating"? If it's a steady current, then there's no time variation in the magnetic field.
  6. Feb 20, 2017 #5
    A steady flow of current, dc, that is being accelerated perpendicular to the electric field by a magnetic field. The current is uninterupted but it must be accelerated as it curves by definition of the lorentz force. Does it produce a varying magnetic field?
  7. Feb 20, 2017 #6
    The charges that make up the current can be accelerating, but if the source current is not changing in time, then the magnetic field won't change in time.
  8. Feb 20, 2017 #7
    Why does it behave differently that a flow of electrons in a vacuum? For example, amplifier tubes use dc and accelerating electrons to produce varying fields.
  9. Feb 20, 2017 #8
    What kind of amplifier tubes are you talking about? If you amplify a DC signal, you get a DC signal.
  10. Feb 20, 2017 #9
    Any tube amp uses ac to modulate dc. A magnetron uses the lorentz acceleration of a static magnetic field to produce em waves. A krlystron uses magnetic fields to modulate dc.
  11. Feb 21, 2017 #10
    Sorry, I got confused. True, accelerating charges will emit EM waves, regardless of if the current is changing. So, you can get time-varying magnetic fields.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Moving charges and varying magnetic fields