On Fri, 16 Jun 2006, Olin Lathrop wrote:

> Peter wrote:
>> I do not see how the potential can be measured when the bar is free
>> standing in a vacuum.
>
> It is not free standing.  One end is held at a known or fixed voltage
> relative to the electron beam electronics.  The voltage at the other end
> will vary depending on the temperature difference between the two ends of
> the bar.

But if it is held (potential wise) then there is at least one junction. 
Is this what you mean ? Say, heat the tip of a grounded pin in vacuum 
and see what happens to an electron beam that passes very near it ? But 
there is already one junction on it, the grounded one. It could be made 
of the same material as the pin, but there still is a junction there.

I think that it would be more interesting to have an unevenly heated pin 
suspended and scanned not with an electron beam but with a vibrating 
reed electrometer. I also think that there will be no measurable 
potential *difference* although the potential should be there ;-)

Peter
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