1. The problem statement, all variables and given/known data A large number, N, of closely spaced turns of wire are wound in a single layer upon the surface of a wooden sphere of radius a. The planes of the sphere are perpendicular to the axis of the sphere (take axis to be horizontal), and turns are uniformly spaced per unit circumference and completely cover the surface. The current in the winding is I. Calculate the magnetic field at the center of the sphere. 2. Relevant equations Ampere's Law. 3. The attempt at a solution I have done a few things. Right now I have made my boundary curve go through the center of the sphere and then up and off to infinity. The part I have concerns about is the shape of the solenoid. Is there any integration I have to do when considering the current enclosed? Is the surface integral just (B)(2a)? Thanks.