Based on the strength of magnetic attractive force to a material or a body, then bodies in this nature are classified into three kinds, those are as follows.
- Ferromagnetic bodies, namely bodies which are strongly attracted by magnets.
- Paramagnetic bodies are bodies which are weakly attracted by magnets. For examples, aluminium, magnesium, platinum, and manganese.
- Diamagnetic bodies are bodies which are not attracted or even tend to be repulsed by magnets. For examples, bismuth, pure zinc, lead, gold, silver, and copper.
Ferromagnetic bodies are widely used as magnets because their magnetic property does not easily disappear, mainly in steel. Meanwhile, based on the ability to store the magnetic property, magnets can be grouped into permanent and nonpermanent magnets.
- Permanent Magnets :Iron, steel alloys, nickel and cobalt are hard metals which are difficult to change to magnets. But, after they become magnets, those metals are able to store their magnetic property for a long time. This ability makes hard metals widely used as magnets. Magnets which are able to store their magnetic property for a long time are called permanent magnets. Permanent magnets are used in an ammeter, voltmeter, cassette tape, disk, and loud speaker.
- Nonpermanent Magnets: Bodies that are not included into hard metals are easily made magnets but they also easily lose their magnetic property. (That kind of bodies is called “soft metal”, eventhough there is no metal that is really soft). Magnets which are made of soft metal are called soft magnets (nonpermanent magnets). One of the examples of nonpermanent magnets is soft iron. The soft iron that is conducted by electric current can change to magnets, but when the electric current is turned off, its magnetic property will disappear. (The method to make magnets by electric current will be studied later).
Irawan,
Etsa Indra dan Sunardi. 2008. Pelajaran
IPA-Fisika Bilingual untuk SMP/MTs. Kelas IX. Bandung: CV.Yrama Widya.
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