How much electric charge do electromagnetic waves carry?

Question

Since electromagnetic waves have both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. How much is that electric charge? Can you possibly get a shock in some way?

You could get a shock if the EM waves kicked electrons off of something and you touched it. But that almost never happens (don't touch leads to large solar panels) — Jim, May 8 at 16:57

Siyuan Ren · Answer 1 · 2012-01-17 14:47:50Z

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Electromagnetic waves are generated from charges and currents, but the former aren't associated with the latter. There is no electric charge "in" electromagnetic waves.

answered Jan 17 '12 at 14:47

Siyuan Ren
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It just makes me wonder how does radio translates them into a message, isn't that the electrons flow through in antenna at receiver end? – Ryan Jan 17 '12 at 14:58

@Ryan Yes, but these are the electrons that are already inside the piece of metal that makes the antenna. The electromagnetic wave provides the electric field which makes the electrons move (more precisely: which biases their movements in the direction of the field since the electrons already move across the metal in random directions). – Adam Zalcman Jan 17 '12 at 16:51

Can I assume that the magnetic field is converted to electric field which causes the electrons to move? Or is the electric field in EMF itself? I think I'm assuming the electric field to be the source of electric charge which is what causing the confusion. – Ryan Jan 17 '12 at 17:31

Indeed, this assumption isn't correct: electric charges generate electric field, not the other way round. They're not the only source of electric field, though. Varying magnetic field generates varying electric field (and vice versa). – Adam Zalcman Jan 17 '12 at 18:50

@Ryan: Electric field is not the source of charges; rather it is the other way around. And contrary to what you think, both electric and magnetic field exert forces on electric charges (minor caveat though, magnetic field does not exert force on stationary charges, nor charges moving parallel to the field). – Siyuan Ren Jan 19 '12 at 9:16

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Adam Zalcman · Answer 2 · 2012-01-17 14:51:47Z

Exactly zero. Electromagnetic waves may be generated by moving charges, but they carry no charge themselves.

Sawi · Answer 3 · 2012-01-17 15:29:45Z

To answer your question,

Electromagnetic (EM) waves carries no electric charge at all. EM waves originate from electromagnetic disturbances, and according to Maxwell's equation, changing electric fields gives rise to magnetic fields, and changing magnetic fields gives rise to electric fields, and so on. That's how EM waves propagate.
You can get a shock if EM waves are strong enough (i.e. the oscillation amplitude is large, which is unlikely), and you have a loop of wire which radius and the EM wavelength are of same order of magnitude. That's how antennas and hypothetical EMP weapons work.

Burning up is also a way of electric fields from waves interacting with matter, our hands for example, never put them in a microwave oven, that would be shock enough. — anna v, Jun 29 '14 at 13:07

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Tuesday, October 27, 2015

How much electric charge do electromagnetic waves carry?

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