Permanent Magnets Vs. Electro Magnets
Difference Between Permanent Magnets And Electromagnets
Magnets and magnetic materials are often divided into two classes: permanent magnets and electromagnets. Permanent magnets are made from materials that remain magnetized even after they are removed from a magnetic field. Iron is the best-known type of permanent magnet. But many other substances can be magnetic. The most powerful magnetic substance known is a chemical compound combining the element neodymium with iron and the very light element boron. The compound produces a magnetic field hundreds of times stronger than a similar piece of magnetic iron.
Electromagnets are coils of wire that become magnetic when electricity passes through them. Sometimes the coils are wrapped around the easily magnetized core of a permanent magnet to increase their strength. Electromagnets are particularly useful. The shape and strength of their magnetic fields can be easily controlled.
To create a very strong field, a very large current is required. Unfortunately, in a coil of normal wire, a large current uses a great amount of energy and produces a lot of heat. To eliminate that problem, the most powerful electromagnets—and the most powerful magnets of any kind—use coils made of a superconductor. A superconductor is a material that carries electricity without any loss of energy. All known superconductors work only at extremely low temperatures. Superconducting coils must be kept chilled in frigid fluids such as liquid helium.