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Thought experiment (all ideal components): Two 1F capacitors wired in parallel (or ring), with open switches separating them, one cap is uncharged, and the other cap is charged with 1 Coulomb->1Volt->0.5Joules (E=CV^2/2). Then close the switches and let the charge equalize. Calculating the new energy in the system results in E=(1F*0.5V^2/2) * 2caps = 0.25J.

Conservation of energy is not violated though, due to the 0.25J being radiated as an electromagnetic pulse.

This blows my mind. You start with a few first principles: 1)conservation of charge 2)some simple properties of an electric field, electrostatics 3)conservation of energy 4) nothing about magnetic fields 5)calculus 6)anything else implicit? ..... and out of this comes a requirement for the existence of magnetic fields and EM radiation!!!!

I'm an electrical engineer, and have a grasp of Maxwell's equations and EM fields and waves... but I'm missing why this result emerges, nothing I see in the first principles hints at B-fields or EM radiation. Can anyone help? And please, don't start high (from the conclusion) and work down, start from my first principles and work up. Thank you!

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  • $\begingroup$ if you conserve energy you might get the new charge to be more on each cap, that may be the correct answer. No radiation I think? $\endgroup$
    – PhysicsDave
    Oct 31, 2018 at 1:34
  • $\begingroup$ PhysicsDave, The principle of Charge Conservation is supported without exception by all empirical observations so far. $\endgroup$
    – Alan Doak
    Oct 31, 2018 at 19:38
  • $\begingroup$ Sorry I should have said voltage ... is there a voltage level where charge and energy are conserved .... this may answer the dilemma. $\endgroup$
    – PhysicsDave
    Nov 1, 2018 at 1:25
  • $\begingroup$ Dave, the voltage on a capacitor is proportional to charge, please stop throwing out random guesses. $\endgroup$
    – Alan Doak
    Nov 1, 2018 at 21:44
  • $\begingroup$ Ok I was going on intuition, not so random, but I see your point now. If you had 10 or even a hundred caps in parallel the energy does dissipate. The E field gets weaker and weaker as the charge spreads over a larger area. $\endgroup$
    – PhysicsDave
    Nov 2, 2018 at 15:35

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You haven't proven the existence of Electromagnetic radiation by your experiment, all you've proved is that energy went somewhere. The next thing you would have to do in your proposed experiment is try to figure out where the energy went, maybe the device heated up, or there was some chemical change. Further experiments are required to rule out such possibilities and detect the electromagnetic wave.

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