Guy,

 

Thanks, and yes it should have been "circa 1886".  I'm still looking for a copy of the actual paper; I don't personally read German, so have to hope another correspondent will identify and copy it for me, perhaps from a collection of Lorentz's papers, etc. somewhere in Germany.  There is another misstatement below your "red mark" also. Kraus's drawing actually shows how some of the field energy from outside the wire is drawn into the wire, to provide the Poynting (diverted and collected) component.  That is specifically not the Heaviside component, which is what is left outside the wire AFTER the Poynting component has been drawn in.  The numbers Kraus places on the contours are only for the Poynting component.

 

Thanks for catching that, and it just shows that all my pencils still need erasers!

 

Best wishes,

 

Tom Bearden

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Reply-To: "Guy A"
Subject: a mistake ?
Date: Mon, 21 Jan 2002 22:21:54 +0100

Hi Tony
 
I think there is an error in the fifth question in : "technical papers - Ten questions......
 
 the error is in red colour

"One can see a neat little illustration of the energy flow surrounding a circuit, in John Kraus, Electromagnetics, 4th edition, p. 578, Figure 12-60, a and b. We cite a 1902 book by Lorentz himself which shows the trick, although he is believed to have advanced in circa 1889-1990 or so. Kraus shows how much of that available but ignored energy flow can be intercepted at each spatial point by inserting a unit point static charge. The more charge one inserts at each point, of course, the more energy one intercepts and diverges at that point."

Guy