This chapter discusses aspects of heat conduction on a rod. At the molecular level, heat energy is caused by the random motion of molecules. When two objects of different temperatures are in contact, the faster moving atoms of the warmer object vibrate against nearby slower moving atoms of the cooler object. This causes the atoms of the cooler object to vibrate more rapidly and in turn effect other slower moving atoms. The motion of molecules results in the warmer objects losing energy and declining in temperature, and the cooler object gaining energy and increasing in temperature. Heat always transfers from warmer objects to cooler objects. This method of heat transfer is called conduction.
Materials that are able to conduct heat are called conductors. Not all materials conduct heat at the same rate. Metals are good conductors because they transfer heat quickly, and air is a poor conductor because it transfers heat slowly. Materials that conduct heat poorly are called insulators, and materials that totally prevent heat flow are called perfect insulators. The coefficient K of heat conduction indicates a material relative rate of conduction compared to silver. Silver has a coefficient of heat conduction of 100.