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

Poynting vector

  1. Jun 7, 2008 #1
    I have a question about the Poynting vector:

    mit.edu/8.02t/www/materials/StudyGuide/guide13.pdf (page 44/51)

    What is the physical interpretation of "S points radially inward". That seems kinda weird. Energy flows to the center?

  2. jcsd
  3. Jun 8, 2008 #2
    Couldn't find your exact page on the link....but yes, seems unusual but that is typical for Poynting vector...say, of a coil or capacitor being charged....the energy flows orthogonally into it from the surrounding space otside the coil.

    Last edited: Jun 8, 2008
  4. Jun 9, 2008 #3

    It's not so weird after all: while being charged, the capacitor is storing energy in the form of the electrical field which is being "built" in the dielectric material inside it. Since the Poynting vector represents a flow of electromagnetic energy, it makes sense that during charging it will point towards the inside of the capacitor, and during discharging it will point outwards. In a stable condition of the capacitor, the Poyting vector will be null.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook