Insulators limit the transfer of heat or electricity. Thermal insulators reduce the rate of heat transfer through materials, while electrical insulators confine electric currents to a designated path. Insulators work by using materials with low thermal or electrical conductivity, such as air, glass, plastic, porcelain, and rubber.
An insulator is a material or method that limits the transfer of heat or electricity. In the case of heat, thermal insulators work by reducing the rate at which heat can travel through a space. Typically, they use specific materials and prevent the movement of heat-carrying matter. In the case of electricity, electrical insulators confine an electric current to a designated path. They typically work by using a material with a lot of external election, a condition that will cause low electrical conductivity.
The first sense of an insulator is the thermal sense. A thermal insulator helps keep an object at the same temperature, hot or cold. It typically works by addressing conduction or convection, which are two modes of heat transfer. Conduction is heat moving through a material whose atoms are stationary; this type refers to the heat that can travel through a solid piece of metal. Convection, on the other hand, is internal heat carried by moving matter; this occurs when the wind carries heat away from your body.
A thermal insulator works by slowing down the rate at which heat can move through a region. The rate of conductive heat transfer is proportional to a material property called thermal conductivity: copper, for example, transfers heat rapidly due to its high thermal conductivity. A good insulator, therefore, has a low thermal conductivity. In fact, air has a low conductivity, but tends to move a lot. Using a blanket acts as a heat insulator because it forces the air to transfer heat by conduction instead of convection.
The second sense of an insulator is electrical. An electrical insulator does not allow electric current to pass because it has low electrical conductivity. Many factors affect electrical conductivity, including temperature, but elements tend to have high or low conductivity. This is because different elements have different numbers of external electrons, which changes how easily those electrons are freed. Metals, for example, tend to have high conductivity because their outer electrons are easy to free.
Many other elements and compounds have large numbers of external electrons, making them difficult to free. This is generally the case with glass, plastic, porcelain and rubber. Therefore, these materials are used in electrical appliances to keep electric currents in a limited path. Low electrical conductivity is also a property of air and many other gases. Air is the only insulator used on elevated power lines.
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