In reply to Robin van Spaandonk's message of Sun, 17 Dec 2006 16:45:46 +1100:
Oops! My mistake. I didn't read carefully enough, and thought you were calculating C*V^2/2 rather than q*V/2. Then I falsely assumed that my own number was farads rather than C! Just goes to show, I should never try using my brain in the afternoon. It just doesn't work right. :( [snip] >In reply to Michel Jullian's message of Thu, 14 Dec 2006 10:21:21 +0100: >Hi Michel, >[snip] >>This made me wonder how much electrical energy would be thus stored in this >>Earth-atmosphere capacitor: >> >>C*V^2/2=q*V/2 = (28 440 * 300 000) / 2 = 4 266 000 000 = 4.3*10^9 J > >You forgot to square the voltage. ;) > >The correct answer is 1.28E15 J. Still only a tiny fraction of what we use on a >daily basis, but then how do we know it takes the Sun a whole day to charge >this >capacitor? > >> >>This is two orders of magnitude less than the 4.3*10^11 J order of magnitude >>estimate at page 20 of this physics lecture material (a good reference for >>capacitor calculations BTW): >>http://galileo.phys.virginia.edu/classes/632.ral5q.summer06/Lecture1-16_Powerpoints/lecture_5_mat/PHYS632_C5_25_Capac.ppt >> >>This energy, according to the same source, is renewed daily by the sun (king >>sized photovoltaic module ;). But even their much higher estimate is still 2 >>million times less than the world's daily energy consumption (about 10^18J), >>very disappointing! >> >>Michel >Regards, > >Robin van Spaandonk > >http://users.bigpond.net.au/rvanspaa/ > >Competition provides the motivation, >Cooperation provides the means. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
