Square current loop (10 + 10 + 10 = 30 points) Consider a square wire loop of side length b = 0.2 m that lies in the xy plane and is centered at the origin. It carries a current I = 1 A that flows counterclockwise if viewed from the positive z axis.
(a) Use symmetry considerations to determine the direction of the magnetic field on the z axis. Note that it is useful to include, in addition to spatial operations like rotations and mirrors, also the time-reversal operation T, which reverses the current and the magnetic field. Note that the symmetry operations form a group, so one can also compose them like m'xy = Tmxy.
(b) Find the magnitude of the exact magnetic field |B| at position (x, y, z) = (0, 0, 0.4) m. Use units of 10^-6 T = μT and state the result to three significant figures.
(c) Find the magnitude of the magnetic field within the dipole approximation |Bdip| at the same position (x, y, z) = (0, 0, 0.4) m. Use units of 10^-6 T = μT and state the result to three significant figures.