
#1
Oct2110, 07:06 AM

P: 5

There is a situation, we have an electric field and a magnetic field, both are static. And we know the density of energy is u=E·D/2+B·H/2, so dU/dt=0, but Poynting vector S=ExH is not zero, which means energy is flowing. This confused me. Static field also has energy flux?




#2
Oct2110, 07:23 AM

Sci Advisor
P: 3,377

Yes, correct. Look also for "hidden momentum".




#3
Oct2110, 08:51 AM

P: 5

can you give me more details？thanks.




#4
Oct2210, 12:04 PM

Sci Advisor
P: 1,250

Poynting vector in static electromagnetic field 



#5
Oct2210, 01:16 PM

Sci Advisor
P: 5,468

[tex]\frac{\partial u}{\partial t} + \nabla \bullet S = J \bullet E[/tex]. Does this help? 



#6
Oct2210, 01:26 PM

P: 5





#7
Oct2210, 01:28 PM

P: 5

And how about "hidden momentum"? I didn't know about this.




#8
Oct2210, 02:45 PM

Sci Advisor
P: 3,377

Probably the best source on these matters is still Jackson's book on Electrodynamics.



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