1. The problem statement, all variables and given/known data A long, straight wire, radius R, carries total current I. The current is distributed in the wire so that the current density is proportional to s, the distance from the center of the wire. (a) Write an expression for the current density J in the wire, as a function of s. 2. Relevant equations J=dI/da 3. The attempt at a solution J=2*s*I/R2 I'm pretty sure my attempted solution is correct because when you integrate J from 0 to R with respect to s you get the total current I. However I kinda just pulled this out of thin air and I'm pretty sure I won't get full marks without showing my work. Is there a different way to do this besides just making up an expression for J like I did?