Show use useful ful permanent magnets P permanent or manent magnets are those that will retain their magnetic properties indefinitely Pro probably babiy their oldest a st and most familiar useful form Is the compass needle according to legend the chinese emperor hoang ti used a magnet in this form to guide his charlot chariot in 2600 B C from this simple beginning permanent magnets have been developed to such an extent that during world war 11 II their use has hag enabled our fighting men to replace bulky heavy equipment with portable models of reduced sue size and weight has made possible hundreds of devices for airplanes and hns has also permitted an increase in the sensitivity of many measuring and electrical communication instruments |