1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I EM Field Angular Momentum Emission Without Emitting Energy?

  1. Dec 30, 2016 #1
    To radiate energy, the Poynting vector must not drop faster than with the inverse square of the distance. Under what circumstances can EM angular momentum be emitted to the vacuum of space (i.e. without being recovered via inductive coupling) and yet not lead to energy losses through radiation? Is it possible?


    Kevin M.
  2. jcsd
  3. Dec 30, 2016 #2
    Say there is a magnet. We bring charge from infinite distance and put it on magnet. Magnetic field give Lorentz force to the charge so we give torque to the field. Thus angular moment is put to electromagnetic field. This is an absorption not a emission but the reverse process, i.e. discharge from charged magnet might be of your interest. Best regards.
  4. Dec 30, 2016 #3


    User Avatar
    Homework Helper
    Gold Member

    I am not sure at all here, but thinking in terms of photons, its like you want a photon to possess momentum but not energy which simply is not possible.
  5. Jan 23, 2017 #4


    User Avatar


    Well... I don't want to full your head with hot air (my mother-language is not English, I don't know if the idiom is correct), but you may take a look to this

    Unruh derived the effect assuming linear acceleration; I think that it is still correct for centripetal.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted