(a) consider a flat sheet of metal foil that is infinite in extent. it carries current, with uniform surface current density k = 200a/m i. determine a formula for the magnetic field due to this current at a distance z from the sheet [6] i. imagine that the sheet is cut to a strip m wide and infinitely long, with the current directed perpendicularly to the long axis. now it is rolled into an infinitely long cylinder of circumference 20cm a. calculate the magnetic field amplitude both inside the cylinder, and outside [4] b. derive a formula for the magnetic vector potential at a distance r from the axis of the cylinder c. briefly discuss the relative merits of the approaches using ampere's law, and using the biot-savart law to part a) of this question