1. The problem statement, all variables and given/known data The current density of a cylindrical conductor of radius R varies as J(r) = J0e−r/R (in the region from zero to R). Express the magnitude of the magnetic field in the regions r < R and r > R. (Use any variable or symbol stated above along with the following as necessary: μ0.) Produce a sketch of the radial dependence, B(r). 2. Relevant equations Ampere's Law [itex]\oint B \bullet ds [/itex] = μ0ienc 3. The attempt at a solution At r < R: B = μ0J(r)A/2∏r J(r) = J0e−r/R J(r)A = J0e−r/R(∏r2) B = (μ0J0e−r/Rr)/2 This is not correct.