How is heat transferred by conduction?

Heat is transferred by conduction through the direct contact and vibration of molecules within a substance.

Conduction is one of the three main methods of heat transfer, the others being convection and radiation. It is the process by which heat energy is transferred within a body or between bodies in direct contact, without the movement of the material itself. This method of heat transfer is most effective in solids, particularly metals, due to their closely packed molecular structure.

The process of conduction begins when a substance is heated at one end. The molecules at this end gain kinetic energy and start to vibrate more rapidly. These vibrations are then passed on to the neighbouring molecules. This process continues along the substance, transferring the heat energy from the heated end to the cooler end. This is often referred to as a 'domino effect'.

It's important to note that during conduction, the heat energy is transferred from molecule to molecule within the substance, but the molecules themselves do not move along with the energy. This is a key characteristic that distinguishes conduction from convection, where the heated molecules themselves move and carry the heat energy with them.

The rate of conduction depends on several factors. Firstly, the type of material: metals are good conductors of heat because they have free electrons that can move rapidly and transfer energy from the hot end to the cool end of the substance. On the other hand, materials like wood or plastic are poor conductors (or good insulators) because they lack these free electrons. Secondly, the temperature difference between the two ends of the substance: the greater the difference, the faster the rate of conduction. Lastly, the dimensions of the substance: the shorter and wider the substance, the faster the rate of conduction.

In summary, conduction is a process of heat transfer that occurs through the direct contact and vibration of molecules within a substance. It is most effective in solids, particularly metals, and is influenced by the type of material, the temperature difference, and the dimensions of the substance.