1. The problem statement, all variables and given/known data Two co-axial, parallel, circular wires of radius R each carrying current I are placed a distance 2d apart. Find an expression for magnetic field B on the axis at distance e from the midpoint between the two loops up to and including terms of 0(e3). 2. Relevant equations The field for one such loop was calculated to be: B = (u0IR2)/(2(z2+R2)(3/2)) 3. The attempt at a solution I'm not sure how the superposition works at all. I've seen it in a few past papers and the method isn't in my notes or the course textbook. (Introduction to Electrodynamics, Griffiths) Any help or hints on the method would be greatly appreciated!