urgent EMM question 1. The problem statement, all variables and given/known data find the vector potential a distance s from an infinite straight wire carrying current I, check that dell dot A=0 and dellxA=B... ok i know the answer is A=A(s) z, in cylindricals. A(s)=(mu*I/2*pi)ln(s/a)z when a is a constant. can someone please explain to me why A points in the same direction as I???? please, i need this asap, because i have no idea.