Chapter 19.1 What is magnetism? Key concepts: What are the properties of a magnet? How do magnetic poles interact? What is the shape of a magnetic field? Key terms: magnet, magnetic pole, magnetic force, magnetic field, magnetic field lines

Properties of magnets A magnet is any material that attracts iron and materials that contain iron. Found originally in a particular kind of rock – magnetite. Magnets repel or attract other magnets. One part of a magnet will always point north when allowed to swing freely.

Magnetic poles Each end of a magnet is a magnetic pole. The effects of a magnet are strongest at the pole. The pole that points north is labeled the north pole. The other pole is labeled the south pole. Magnets always (almost always) have two poles. Like poles repel, unlike poles attract. The attraction or repulsion between them is called the magnetic force.

Magnetic fields The area of a magnetic force around a magnet is known as its magnetic field. Magnetic field lines are invisible (imaginary) lines that map out the magnetic field around a magnet. The lines spread out from one pole, curve around a magnet, and return to the other pole. The lines form two complete loops from pole to pole and never cross. The distance between the lines indicates the strength of the field. Closer together means stronger.

Bill Nye: Magnetism http://www.youtube.com/watch?v=4bppssq4jsI