EMM Lesson 5 MAGNETIC FORCES

Notes Magnetism is one of the most interesting mysteries of the natural world. It can Levitate objects Act through solid object including human hands Pull on things without touching them

Notes Magnetism makes Electric motors spin Loudspeakers and earphones work Refrigerator doors stay closed Televisions, video records and household electricity (produced by electric generators) possible.

Notes Permanent magnets all share a common characteristic: they must contain either iron, nickel, cobalt or a combination of these elements. The exert forces on other magnets and can attract other materials that become magnetized in the presence of a permanent magnet.

Notes Permanent mangets have a north and a south pole. The north pole of a magnet is attracted to the magnetic pole in the northern hemisphere of the earth. A suspended magnet will align itself so that its north pole points to “magnetic north”. Loadstone is a natural permanent magnet.

Notes When two magnets are placed near each other, a force of interaction is exerted between them. Like poles (north-north or south-south) will repel one another. Opposite poles (north-south) will attract one another. “Opposites attract, likes repel”.

Notes The force of interaction depends on the distance between the magnets. The closer two poles are placed to one another, the stronger the force of interaction, and this decreases as they are moved further apart.

Notes The space around a magnet is called a “magnetic field” because it can influence objects without touching them. The field is the region around the magnet in which magnetic forces will act on objects.

Notes Some objects are not naturally magnetic but become magnetic in the presence of a magnetic field. These materials are called paramagnetic. Example: Paper clip Not all metals are attracted to a magnet. Ex: aluminum foil

Notes Why are only certain metals attracted to a magnet? Why are some seemingly nonmetallic objects also attracted?

Notes Flexible magnets are made of rubber and plastic and may contain tiny particles of iron or ferrite. Ex. Audiotape and videotape On flexible magnets, one flat side is the north pole and the other is the south pole. If you put two flexible magnets together with the north pole stuck to the south pole, it will create a single, stronger magnet

Vocabulary attraction compass constant magnet magnetism magnetic pole repulsion