Heat is transferred through conduction, convection, and radiation, but only heat can be transferred. Metals are good conductors, while wood, paper, air, and cloth are poor conductors. Insulators, such as air, prevent heat transfer. Charged objects can transfer charge through conduction.
Heat is transferred in several ways, conduction, convection and radiation. Regardless of the transfer method, only heat can be transferred. Cold is simply the absence of heat and cannot be transferred by any method.
Conduction is the transfer of heat from one molecule to another through a substance. Not all substances conduct heat at the same rate. Metals are considered good conductors as they can transfer heat quickly. Stone is also a moderately good conductor, but wood, paper, air, and cloth are poor conductors of heat.
Various materials are often studied for the way they conduct heat. Materials are given numbers indicating their relative speeds of conduction. Each material is compared to silver – the standard – which has a heat conduction coefficient of 100. Other products run up the heat conduction coefficient scale. Thus, copper has a coefficient of 92, iron 11, water 12, wood 03, and a perfect vacuum has a coefficient of conductivity of zero.
Different conduction rates can be seen in people’s daily lives. For example, when a cloth pot holder is wrapped around the handle of a metal pot or frying pan, heat is not transferred to the person’s hand. A cloth pot holder works because it is a poor conductor of heat. Also, some pot or pan manufacturers design the handle to be made of a low-conducting material, such as wood.
Another name for materials that are poor conductors of heat is insulators. Air is a great insulating material when enclosed in an enclosed space. It also only has a conductivity coefficient number of .006. In fact, one of the things that makes clothing made of wool, fur, feathers, and loose fibers so warm is the fact that the air trapped between the feathers, fur, or fibers is a great insulator.
As mentioned earlier, an insulator does not allow electrons to move freely along it. This prevents it from getting hot to the touch; alternatively, metals allow electrons to move around easily. Consequently, if a charged rod touches an isolated metal object, some of the charge will pass and the metal object receives a charge by conduction. The charge will cover the entire surface of the conductor. So if the charged object touches a large body via a wire, it gets grounded and loses its charge.
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