Distinguish between the following:
(a) permanent magnets and temporary magnets.
(b) magnetic and non-magnetic materials.
Answers
Permanent Magnets
Permanent magnets differ from temporary magnets by their ability to remain magnetized without the influence of a nearby external magnetic field. Typically, permanent magnets are made from "hard" magnetic materials where "hard" refers to a material's ability to become magnetized and remain magnetized. Steel is an example of a hard magnetic material.
Temporary Magnets
Unlike permanent magnets, temporary magnets cannot remain magnetized on their own. Soft magnetic materials like iron and nickel will not attract paper clips after a strong external magnetic field has been removed.
One example of an industrial temporary magnet is an electromagnet used to move scrap metal in a salvage yard. An electric current flowing through a coil that surrounds an iron plate induces a magnetic field that magnetizes the plate. When the current flows, the plate picks up scrap metal. When the current stops, the plate releases the scrap metal.