# Resistance of a sphere of resistivity rho and radius S

1. Nov 28, 2004

I calculated the resistance between two points (P and Q) on a sphere that are located on the two ends of a diameter by dividing the sphere into thin strips of thickness dz that are in series perpendicular to the line PQ (say the z-axis). I can get an expression for the indefinite integral in theta (the polar angle theta, z = S Cos (theta), and S= radius), however I run into problem when evaluating this definite integral for theta = 0 to pi. Apparently the fact that the strip element becomes a points at the ends is causing this problem. I use dR=rho * dl/A with dl = -S Sin(theta) d(theta) and A(theta) = pi {S Sin(theta)}^2. What is going wrong here? Because I know that there must be a finite resistance between two such points.

2. Nov 29, 2004

### ardcarlos

I need help!

I'm a spanish coach from Barcelona and I have a problem.

I need some information about "curve fenomenon" in velodrom cycling. When a cyclist go into a curve power is less than in straight and velocity is high to a straight. Please do you explain this fenomenon?.

My e-mail is ardcarlos@hotmail.com

Thank you very much!