# Why is cobalt used in magnets

## Understand physics 4, textbook

42 3  Workbook, page 20 Magnets and magnetic poles 1. What are the properties of magnets? Magnetic or not? (Fig. 42.1) E1, E2 Hold a magnet over a bowl with various objects, eg toothpicks, nails, erasers ... Which materials are attracted and what do they have in common? A magnet attracts objects made of iron, for example. The attraction works mutually. For example, a piece of iron can also attract a magnet. Materials that are attracted to the magnet like iron are called ferromagnetic materials. This also includes (at room temperature) the elements nickel and cobalt. Permanent magnets (permanent magnets) are pieces of ferromagnetic alloys that do not lose their attraction. They are made from AlNiCo (an iron alloy with aluminum, nickel and cobalt), samarium-cobalt (SmCo) and neodymium-iron-boron (Nd 2 Fe 14 B). 2. What are magnetic poles? The strongest parts of the magnet (Fig. 42.2) E1 Put a bar magnet in a box full of small nails and then lift it up. Where do the nails mainly get caught? The small nails mainly get caught on the two ends of the bar magnet. The "strong" ends are called magnetic poles. The “floating” paper clip (Fig. 42.3) E1 Hold a strong magnet in a tripod. Tie a paper clip to a thin thread (e.g. twine, fishing line) and attach the other end to a large piece of mass. Try to bring the paper clip close enough to the magnet that it "floats". There should be as large a space as possible between the paper clip and the magnet. The paper clip "floats" in the immediate vicinity of one of the two magnetic poles. It looks like it is pointing there. V1 42.1 Magnetic or not? A magnet attracts ferromagnetic substances such as iron, nickel and cobalt. There is a mutual attraction between a magnet and ferromagnetic materials (e.g. iron, nickel and cobalt). M V2 42.2 The strongest parts of the magnet V3 42.3 The “floating” paper clip The two parts of the magnet with the strongest attraction are called magnetic poles. M 42.4 The colors of these magnetic toys do not indicate the poles! Horseshoe or U magnet Ring magnet Bar magnet 42.5 Depending on the application, magnets are produced in different shapes. 42.6 The foil on refrigerator magnets contains, for example, iron powder. Info box: Magnetic poles are just the ends of the magnet. Whole parts of magnets are often colored for better visibility: North pole side: Red South pole side: Green For testing purposes only - property of the publisher öbv