Heat is transferred in several different ways, either conduction, convection, and radiation. Regardless of the method of transfer, 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 speed. Metals are considered good conductors since they can speedily transfer heat. Stone is also a moderately good conductor, but wood, paper, air, and cloth are poor heat conductors.
Various materials are often researched for the way they conduct heat. The materials are given numbers that tell their relative rates of conduction. Each material is compared to silver – the standard – which has a coefficient of heat conduction of 100. Other products travel down the heat conduction coefficient scale. So, copper has a coefficient of 92, iron of 11, water of .12, wood of .03, and a perfect vacuum has a conduction coefficient of zero.
Different rates of conduction can be seen in people’s everyday 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 heat conductor. In addition, some pot or frying pan manufacturers design the handle so that it is in a material that has a low conduction coefficient – such as wood.
Another name for materials that are poor conductors of heat is insulators. Air is a superb insulation material when it is locked within an enclosed space. It only has a conduction coefficient number of .006, as well. In fact, one of the things that makes wool clothes, fur coats, down feathers, and loose fibers so warm, is the fact that the air locked between the feathers, fur, or fibers is a great insulator.
As mentioned above, an insulator does not allow electrons to move freely along it. It is thereby prevented from becoming hot to the touch; in the alternative, metals do allow electrons to move readily. Consequently, if a charged rod touches an insulated metal object, some of the charge will pass and the metal object receives a charge via conduction. The charge will cover the total surface of the conductor. Then, if the charged object touches a large body via a wire, it becomes grounded and looses its charge.
By Deanna Baranyi