Note:  Do not rely on this information. It is very old.

Compound Magnets

Compound Magnets. When a solid piece of steel is magnetised we find that the external surface is much more intensely affected by the magnetising influence than the interior, and it is difficult to render the whole mass uniformly magnetised. If, therefore, a powerful magnet is to be manufactured, it is usual to build it up of thin strips or rods of separately-magnetised steel, the whole bundle being then bound together or the pieces fixed parallel to each other on a suitable framework. Such an arrangement is called a compound magnet; it is stronger than the simple magnet, and retains its magnetism more permanently.