Dave wrote:
chuck wrote:
Dave wrote:

Cecil Moore wrote:

Dave wrote:

Cecil, as an engineer you should stick with standard vocabulary.



Just trying to appease the physicists, Dave. They are
arguing that it is not power until work is done.


A Poynting vector is watts/square angle [watts/degree^2]. It is not
being dissipated in free space. It is Diverging [vector
relationship]. How do the physics type adjust their definition to
include the Poynting Vector?

I'll sit back and read the follow up posts for the next few weeks :-)



And now one for the engineers!

How do you interpret a non-zero Poynting vector determined by static
E- and H- fields?

73,

Chuck


Static fields, by definition, do not have a time varying divergence. No
time variation, no Poynting Vector. Nes Pas?


I think the Poynting vector can be calculated even when the E and H
fields are static. Of course, doing so would violate Poynting's
assumptions and thus be meaningless. But if one didn't know in advance
that an arbitrary closed surface contained static sources, and he found
the Poynting vector, S, for some small area, he could well get a
non-zero answer. Of course, the integral of S over the entire surface
would always be zero in the case of static sources.

To be applicable, the Poynting theorem requires that the E and H fields
arise from a single source, satisfying Maxwell's first two equations.
But that information may not be known in advance.

73,

Chuck








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