How Is J₀ Calculated in a Wire with Nonuniform Current Density?

[splac6996]

A long, straight conducting wire of radius R has a nonuniform current density J=J$$_{}0$$*r/R , where J$$_{}0$$ is a constant. The wire carries total current I .Find an expression for J$$_{}0$$ in terms of I and R .

 

[pam]

You have to integrate: $$I=2\pi\int_0^R Jrdr$$.