I was reading the following thread at stackexachange. http://physics.stackexchange.com/qu...e-electrostatic-force-does-wire-thickness-mat The first answer calculates the radial force using the capacitance of ring. Any ideas how the poster derived the formula for capacitance? Is the formula different for MKS units? I am interested in deriving it if it doesn't involves too much of mathematics. Any help is appreciated. Thanks!