It's OK Robin, it happens to me all the time :) Your other point is valid though, we don't know how long it takes the Sun to charge this capacitor. But it's unlikely it charges it in one two millionth of a day = 43 ms, which would be required for it to provide the world's daily energy consumption :/
Michel ----- Original Message ----- From: "Robin van Spaandonk" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Sunday, December 17, 2006 7:10 AM Subject: Re: [Vo]: Re: Going Van de Graaff > 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. >
