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*To*: tesla-at-pupman-dot-com*Subject*: Re: "human" topload*From*: Terry Fritz <twftesla-at-uswest-dot-net>*Date*: Sun, 10 Sep 2000 19:36:45 -0600*Delivered-To*: fixup-tesla-at-pupman-dot-com-at-fixme*In-Reply-To*: <005e01c0190e$85a455b0$60064f89-at-empyrean.jpl.nasa.gov>

Hi Jim, At 01:59 PM 9/7/00 -0700, Jim Lux wrote: snip... >For what it's worth, a sphere 1 meter radius in free space has a capacitance >of about 110 pF. If it is close (within 5 radii) of a grounded surface, the >C is going to rise. The mathematically inclined (and masochistic) can do >this by considering the ground as a reflector and calculating the >capacitance between two spheres separated by 2d, where d is the distance to >ground. This in itself is non trivial (there isn't a closed form solution). snip... Actually, a single graph would do it all. The only defining aspect to the capacitance of a sphere above an infinite plane is the diameter to distance factor. So if you knew the capacitance of a 1 meter ball 1 meter above a plane, the capacitance if a 1/2 meter ball 1/2 meter above the plane would simply be 1/2 of the 1 meter ball's capacitance. A chart with a normalized 1 meter ball's capacitance vs. distance above the plane could be used for any diameter sphere just by multiplying the capacitance by the diameter factor. A toroid is a bit different, but the answers would probably still be close. The terminals we use are far enough above ground that this effect would probably not be significant. E-Tesla5 does this stuff already taking into account the other TC variables, so the generation of such a chart would probably not be useful to us... Cheers, Terry

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