----- Original Message ----- From: "Horace Heffner" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, August 13, 2007 4:40 PM Subject: Re: [Vo]:Re: Only potential differences matter
> > On Aug 13, 2007, at 2:59 AM, Michel Jullian wrote: > >>> Measuring relative surface potentials between two >>> electrodes simply doesn't tell you if there are excess surface >>> electrons on one or both or neither. It still seems pretty obvious >>> to me. >> >> You can say that three times it won't make it true, whatever Lewis >> Carroll says ;-) >> >> Come on, what you describe is a capacitor, there are excess >> electrons on the surface of the most negative electrode facing the >> most positive one, of a very predictable total charge given by: >> >> C*Delta_V = C*(potential of most positive electrode - potential of >> most negative electrode) >> >> Elementary EE stuff. Only potential differences matter I tell you! > > Suppose a 1 m radius metal sphere, sphere A, has 1 coul more negative > charges than positive. Suppose a 1 m radius metal sphere, sphere B, > has 2 coul more negative charges than positive. They have a finite > potential difference V at some separation D. The same is true for > two spheres X and Y where X has 2 coul less negative charges than > positive, and Y has 1 coul less negative charges than positive. > > Sphere, charge in coul: > A -1 > B -2 > X +2 > Y +1 > > There is no difference in relative potentials, How do you know? All you can tell is that there is no difference in relative charges! Also note that in practice, the spheres would start as neutral (zero net charge), and the power supply would transfer electrons from one to the other so that your two spheres would have equal and opposite net charges at all times. Michel > but the two differ > significantly in electron fugacity, the significant variable.
