1. The problem statement, all variables and given/known data A long, straight, copper wire has a circular cross section with radius R, resistivity p and permittivity ε. If the current through the wire at any time t is sin(ωt) amperes, find the magnitude of the magnetic field B at time t a distance r from the centre of the wire for r > R. 2. Relevant equations Ampere's Law: μI = ∮B•dl Possibly Law of Biot-Savart: B = μ/4π * (Idl x r)/r^2 3. The attempt at a solution μI = ∮B•dl μ(sin(ωt))=∮B*dl (Since they are parallel) μ(sin(ωt))=B∮dl (Since B is constant radially around conductor) This is where I reach a bottleneck. I don't know how to incorporate ε (since this is a magnetic field). I assume resistivity would be used in calculating the current I, but I don't know how that ties into the sinusoidal function.