Using the theory of Biot-Savart, derive an expression for the magnetic field at the center of a square coil of side d, current I, and with N turns. To do this, you must first derive an expression for the magnetic field of a wire of length d, at a point along a line perpendicular to it and through its midpoint. This analysis is done in Section 28.3 of the textbook, and in the associated lecture notes (Sources of Magnetic Field: Biot-Savart). Then, simply use the summation of vectors to determine the net field at the center of a square (i.e., due to the four wires together). Complete this analysis on a separate sheet of paper. Fill in your data table with these predictions. (in the BL predicted column.)