Difference Between Insulators And Semiconductors And Superconductors
Metals are good conductors of electricity. That is, they offer little resistance to its flow. Some metals, such as copper, are especially good conductors. Pure water is a poor conductor. But when some substances, such as salt, are dissolved in it, it conducts electricity well.
Many other natural substances, such as most rocks and minerals, have a lot of resistance. They can scarcely be made to conduct electricity. These substances, and human-made substances such as glass and plastic, are such poor conductors that they are often used as insulators. These substances can protect people from accidental contact with an electrical current. Insulators are used to wrap metal wires that carry an electric current, for example.
The electrical resistance of an object is affected not only by what material it is made of, but also by its shape.
Some materials can conduct an electric current under conditions that can be controlled. They are called semiconductors. The ability to control the flow of electric current is the most important property of semiconductors. This property makes them useful in modern electronics.
Certain materials, called superconductors, lose all electrical resistance when cooled to very low temperatures. They have made it possible to create powerful electromagnets. One use for these magnets is in magnetic resonance imaging (MRI) scanners. These devices let doctors see detailed images of the inside of the brain and other body organs.
Scientists are trying to create materials that are superconductive at high temperatures. These materials could be used to transmit electric power over long distances more efficiently.