The figure above (right) shows a cross-sectional view of a coaxial cable. The center of the conductor is surrounded by a rubber layer, an outer conductor and another rubber layer. In a particular application, the current in the inner conductor is I1= 1.00 A out of the page and the current in the outer conductor is I2 = 3.00 A into the page. Assuming d = 1.00 mm, determine the magnitude and direction of the magnetic field at point a.
ans:200 μT towards top of page;
The Attempt at a Solution
If we consider the field at a by virtue of I1, then ∫Bds=I1/μ
B=200μT which is the answer. But we have not yet considered magnetic field due to I2. I suspect that B field due to I2 is 0 but can't get it.