A magnetized sewing needle has a magnetic moment of u = A ? m2. At its location, the Earth's magnetic field is b = T northward at th = below the horizontal. Identify the orientations of the needle that represent
(a) the minimum potential energy and
(b) the maximum potential energy of the needle field system.
(c) How much work must be done on the system to move the needle from the minimum to the maximum potential energy orientation?