2 - Role of Magnetism and Magnetic Materials in Modern Society

Summary

Magnets have been used in society for centuries. In ancient times they were considered paranormal or mysterious substances. Nobody knew how or why the magnets attracted certain but not all materials. As we have seen in Chapter 1, it was not until the seventeenth century that there was considerable understanding of electromagnetism and a progressive increase in the use of magnetic materials as useful functional materials. Nowadays magnets are all-pervasive in modern society, starting from home to medical applications, to transport, and industrial sectors (Fig. 2.1).

We utilize magnetism all over our homes although it may not be very obvious. Electric motors create force by using electricity and magnetic fields. So nearly all household appliances such as fans, washing machines, vacuum cleaners, and blenders that use electricity to create motion invariably have magnets. Many households have small magnets holding paper notes or small items to the metal refrigerator door. While some magnets are visible, the others are hidden inside various items and appliances such as computers, cellphones, DVDs, iPods, cameras, sensors, doorbells, and toys of children. The dark stripe on the backside of credit cards is a magnetic strip storing the relevant data of the cardholder.

Computers use hard disk drives to store information. Hard disks are memory devices where magnets alter the direction of magnetic material on disk segments. Information is processed in computers in binary language, the base-2 units of which correspond to a magnetic field aligned to either the north or the south. These fields are spun in a hard disk, and a magnetic sensor is used to read these. Inside the small speaker found in computers, televisions and radios, electrical signals are converted into sound vibrations by wire coil and magnet.

Magnets are used profusely in the industrial world. Mechanical energy is converted into electricity with the use of magnets in electric generators. On the other hand, motors use magnets to convert electricity back into mechanical work. Sorting machines using magnets are deployed in mines to separate useful metallic ores from crushed rock. In the food processing industry magnets are used for removing small metallic particles from grains and other food.