11.0 MAGNETISM

Magnetism is a fundamental force of nature. It is the property of certain materials to attract or repel other materials. This chapter explores the behavior of magnets, the concept of magnetic fields, how materials become magnetized, and the Earth itself as a giant magnet. Understanding magnetism is essential for motors, generators, compasses, and countless modern devices.

11.1 PROPERTIES OF MAGNETS

11.1.1 Magnetic Poles

A magnet has two regions where the magnetic force is strongest, called poles. These are the north-seeking pole (N) and the south-seeking pole (S). If a magnet is freely suspended, the north pole points towards the Earth's geographic north.

Fundamental law: Like poles repel (N-N or S-S), unlike poles attract (N-S).

11.1.2 Magnetic and Non-magnetic Materials

• Magnetic materials: These are materials that are attracted to a magnet. They include iron, steel, nickel, cobalt, and some alloys. They can be magnetized (turned into magnets).
• Non-magnetic materials: These are materials that are not attracted to a magnet. They include wood, plastic, glass, copper, aluminum, paper, etc. They cannot be magnetized.

Note: Being magnetic is different from being a magnet. A magnetic material can be attracted to a magnet, but it is not itself a permanent magnet (unless magnetized).

11.1.3 Testing for Polarity

To