(a) In Section 27.7 we discussed how a magnetic dipole, such as a current loop or a magnetized object, can be attracted or repelled by a permanent magnet. Use this to explain why either pole of a magnet attracts both paramagnetic materials and (initially unmagnetized) ferromagnetic materials, but repel. Diamagnetic materials.
(b) The force that a magnet exerts on an object is directly proportional to the object's magnetic moment. A particular magnet is just strong enough to pick up a cube of annealed iron
(Km = 1400) 2.00 cm on a side so that the iron sticks to one of the magnet's poles; that is, the magnet exerts an upward force on the iron cube equal to the cube's weight. If you tried to use this magnet to pick up a 2.00-cm cube of aluminium instead, what would be the upward force on the cube? How does this compare to the weight of the cube? Could the magnet pick up the cube?
(c) If you tried to use the magnet to pick up a 2.00-cm cube of silver, what would be the magnitude and direction of the force on the cube? How does this magnitude compare to the weight of the cube? Would the effects of the magnetic force be noticeable?