# hollow section 0 to R R

Question

1. A hollow cylinder of length L, inner radius R1 , and radius Ris filled with two different materials. From Rto R2, the space is filled with a material of resistivity p. From Rto R, the space is filled with material of resistivity p

a) Derive an equation for the resistance of this structure as current flows from Rto R3 (ALONG the radial direction, NOT along the length). Ignore edge effects.

b) If the total voltage across the object is Vo, find an expression for the current density along the objects ( i.e. find J(r)).

Take V= Vo  at R1   and  V=0 at R3