Electromagnets have any number of applications in modern technology. You can find electromagnets in all kinds of electronic equipment, including many of the devices you use every day. They also are used in medicine and in industry. In fact, it's fair to say that electromagnets are what has made the majority of modern technology possible: they allow electricity to be used as a force, just as wind and water are.
The electromagnet is the key component of an electric motor. The driveshaft of the motor is attached to an armature with one or more coils of wire wrapped around it. This creates an electromagnet. A field magnet is used to create a steady magnetic field with a fixed polarity. When the motor is turned on, the forces between the electromagnets and the field magnet drive the shaft around, creating movement.
Usually the magnet in a speaker is a permanent magnet but sometimes it is an electromagnet. The current through the electromagnet varies, causing movement between it and the speaker diaphragm. The vibration of the speaker produces sound.
Electromagnetic cranes use a high-power electromagnet to lift heavy loads. The load has to have enough metal in it for the electromagnet to pick it up. Electromagnetic cranes are widely used in the scrap metal industry or other fields where large amounts of metal must be moved.
Magnetic Separators in Industry
Magnetic separators have various industrial applications. One of the most important is in mining. A mixture of different materials, some magnetic and some not, is passed through the separator. The electromagnet attracts only those that are magnetic. By varying the strength of the current flowing through the electromagnet, materials with different degrees of magnetism can be separated.
Magnetic Separators in Research and Medicine
Magnetic separators are used in research. They are used to analyse substances, by drawing out materials that are either already magnetic or have been "tagged" using a substance that magnetises them. Magnetic separators also can be used to separate red blood cells out of whole blood.
Magnetic resonance imaging involves using electromagnets to create a powerful magnetic field around the patient. This forces all of the magnetic fields of the atoms in the patient's body into a single alignment. The machine sends powerful radio waves through the patient's body. This forces some of the atoms in the patient's cells into a new position. As they move back, they send tiny radio signals of their own. These signals are used to build up a complete picture of the patient's tissues.
Maglev stands for magnetic levitation. Maglev trains use electromagnets so that they are literally floating above their tracks. This greatly reduces friction and allows the trains to move at tremendous speeds.