A very long, cylindrical wire of radius R carries a current wire. (a) Use Ampere's law to find the magnetic field inside of the cylinder at distance, r, from it how magnetic field lines look like inside of the cylinder. (b) Calculate the magnetic flux of that magnetic field of the that has one side of length W running down the center of the wire and another side of length R, as shown in figure below (shaded rectangle). [Hint: use integration method ].
