[TCML] Re: Re: Spark models, revisited

["Udo Lenz" <udo_lenz@xxxxxxxxxxxxxx>]

If I apply the equations for a wire of 0.2 mm diameter 1 m
above a conducting plane from
http://en.wikipedia.org/wiki/Capacitance
I get 5.6 pF/m. For 11.1 pF/m I would need wire diameter of 2.7 cm.
Antonio Carlos M. de Queiroz wrote:That formula doesn't work if the distance 
of the plane is large (gives zero capacitance). A better approach is to 
consider the capacitance of a thin toroid in free space, that can be 
calculated exactly (discussions in the archives of the list, years ago) and 
divide the capacitance by the toroid circunference.
A neat trick and you are right about beingcareful which formula should be 
used. The wiki pagegives at its end an equation for infinitely 
distantplanes. For my 70cm arc at 0.2mm diameter it works outto 6.5pF/m, 
which is more than the value I gave abovebut not really enough to get the 
currents and powerdissipation in the arc at the voltage I run on.Udo 

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