Magnets have the ability of attracting magnetic materials and attracting or repelling other magnets--making them perfect for inducing motion. Furthermore, their magnetism is also used to induce electricity. An electric current through magnetic material can also induce magnetism into it, making it a temporary magnet useful to perform many tasks. In computers, magnets have many uses.
Hard Disk Drives
Data are stored in hard disk drives on the basis of magnetism. The surface of the disk is coated with magnetic material that consists of billions or even trillions of tiny magnets. Computer circuit components are able to process data in terms of whether current is present or not, represented by a 0 or 1. The north and south poles of the tiny magnets on the surface of hard disk drives can represent either 0s and 1s, making them perfect for computer data storage. An electromagnetic head is used to store data into these cells since an electromagnet can reverse its own polarity by reversing the direction of current flowing through it--enabling it to rearrange the polls of the tiny hard disk drive magnets. The same head can also read the data stored on the hard disk drive.
Most of the computer monitors in use today employ CRT (cathode ray tubes) as their display technology. These are glass vacuum tubes with an electron gun on one end and a florescent screen on the other that becomes illuminated when an electron beam fired from the electron gun strikes it. The electron beam is accelerated and deflected by an electromagnetic field (powered by magnets) before it strikes the screen, thus effectively forming an image. The deflection is carried out depending upon the input display signals received by the monitor and those signals alter constantly, thus enabling animated video display.
A motor is an essential part of an electrical fan, and all motors contain magnets since they use magnetism and electricity to induce motion. In computers, fans are used primarily for cooling purposes and are mounted on all major heat-generating computer components including the processor, the power supply and high-end graphic cards. In some custom-built computers, there may be additional fans in the casing to provide enhanced cooling and ensure smooth performance. Without these fans, the excessive heat generated causes significant degradation of the computer's performance and even results in equipment failure.
Optical Disc Drives
Moving parts of computers like the lens and the eject mechanism of optical disc drives require motors to enable their motion and thus, involve the use of magnets since all motors operate using magnets.