Re: wrong divergence?!?

*To*: mathgroup at smc.vnet.net*Subject*: [mg6384] Re: wrong divergence?!?*From*: "Edward G. Neuman" <edneuman at math.siu.edu>*Date*: Sun, 16 Mar 1997 19:24:48 -0500 (EST)*Organization*: Unknown Organization*Sender*: owner-wri-mathgroup at wolfram.com

peter <psalzman at landau.ucdavis.edu> wrote in article <5gagic$g02 at smc.vnet.net>... > > hi all > > when i take the divergence of: > > e = {q/r^2, 0, 0} > > i get zero. i remembered to load VectorAnalysis and SetCoordinates to > Spherical. > > this is the electric field due to a point charge at the origin. even > though MMA doesn't know maxwell's equations, if we strip all the physical > meaning from this vector field, shouldn't the divergence be something other > than zero at the origin? > > thanks! > > peter > -- > Birthdays are good for you: A federal funded project has recently determined > that people with the most number of birthdays will live the longest..... > -=><=-+-+-=><=-+-+-=><=-+-+-=><=-+-+-=><=-+-+-=><=-+-+-=><=-+-+-=><=-+-+-=>< =- > I BOYCOTT ANY COMPANY THAT USES MASS ADVERTISING ON THE INTERNET > > > Function Div returns a correct value. To check it calculate divergence in spherical coordinates to obtain: div (q/r^2, 0 , 0) = (1/r^2) * D[(r^2) * (q/r^2), r] = (1/r^2) * D[q,r] = 0. I assume that q does not depend on r. I hope this helps. ==================================================== Edward Neuman E-mail: edneuman at siu.edu http://www.math.siu.edu/neuman/personal.html