A long straight vertical wire of circular cross section of radius $$R$$ contains $$n$$ conduction electrons per unit volume. A current $$I$$ flows upward in the wire. The expression for magnetic force on an electron at the surface of the wire is, assuming all the conduction electrons are moving with drift velocity,

A

$$\frac{\mu_0}{4\pi^2}\frac{I^2}{nR^3}$$ outward

B

$$\frac{\mu_0}{2\pi}\frac{I^2}{nR^3}$$ inward

C

$$\frac{\mu_0}{2\pi^2}\frac{I^2}{nR^3}$$ inward

D

$$\frac{\mu_0}{2\pi^2}\frac{I^2}{nR^3}$$ outward