Andy Talbot pisze:
Here's an interesting little thought excercise
Consider the Earth as one plate of a capacitor, and the lower surface
of the ionosphere as the other. Without actually doing the
calculation, what do you 'feel' the capacitiance might be?
Then do the calculation; the result is rather surprising
Dear Andy, LF
as i had completely no idea what might be the value of such defined
capacitance
i immediately thought that this "interesting little thought excercise"
could be added to
my sunday evening cup of coffee ... :)
Gauss theorem says that E field from charge Q on a sphere of radius R is
E = Q/(4*pi*eps*R*R)
having now two spheres: inner (earth) R1 and outer: ionosphere R2
the potential V = integral from R1 to R2 over EdR which immediately gives
V = (Q/4*pi*eps)*(1/R1 - 1/R2) so as C = Q/V one gets
C = 4*pi*eps/(1/R1 - 1/R2)
assuming R1 = 6370km ; R2 = 6370km + 60km = 6430 km; eps = 8.854*10^-12 F/m
C is about 0.076F or 76 miliFarad
pse, check my "homework" :) Piotr, sq7mpj
qth: Lodz /jo91rs/
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