Permanent Magnets

A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. This field is present even when there is no external magnetic field being applied. The most common types of permanent magnets are made from materials such as iron, nickel, cobalt, and some rare earth metals.

Magnetic Properties of Permanent Magnets

Permanent magnets have several key properties:

• Remanence: The strength of the magnetic field that remains in the magnet after an external magnetic field is removed.
• Coercivity: The resistance of a material to becoming demagnetized. A higher coercivity indicates a stronger resistance to demagnetization.
• Curie temperature: The temperature at which a material loses its magnetic properties.

Types of Permanent Magnets

There are several types of permanent magnets, including:

1. Alnico Magnets: Made from aluminum, nickel, and cobalt, with the addition of iron and other elements. They are known for their strong magnetic properties.
2. Ferrite Magnets: Made from a ceramic compound consisting of iron oxide and other metals. They are relatively inexpensive and are widely used in household appliances and electronics.
3. Neodymium Magnets: Made from an alloy of neodymium, iron, and boron. They are the strongest type of permanent magnet available commercially.

Applications of Permanent Magnets

Permanent magnets are used in a wide range of applications, including:

• Motors and generators
• Sensors
• Speakers and headphones
• Magnetic therapy
• Magnetic separation

Study Guide

Here are some key points to focus on when studying permanent magnets:

1. Understand the properties of permanent magnets, including remanence, coercivity, and Curie temperature.
2. Be able to identify and describe the different types of permanent magnets, such as alnico, ferrite, and neodymium magnets.
3. Explore the various applications of permanent magnets in real-world devices and technologies.
4. Consider the environmental and social impacts of mining and producing rare earth magnets, such as neodymium magnets.

By understanding the properties, types, and applications of permanent magnets, you will gain a comprehensive knowledge of this important aspect of magnetism and its practical uses.