Understanding Conduction and the Heat Equation

Thanks to CuriosityStream for sponsoring this video. When any object is heated, like the rotor in a car disc brake for example, which gets hot because of friction, the distribution of temperature within the body will change as thermal energy flows from hotter to colder areas.

This re-distribution of thermal energy is called thermal conduction. It's one of three ways in which heat transfer can occur, along with convection and radiation. Understanding conduction is really important for so many engineering applications, so let's learn more about it! On the molecular scale thermal energy is really just the random motion of the atoms and molecules

that make up an object. As temperature increases the motion becomes more and more significant, and close to absolute zero there's barely any motion at all.

Because the atoms of a material are connected to each other by bonds, forming a lattice structure, vibrations of the atoms travel through the lattice, which results in thermal energy being redistributed from areas of higher energy to areas of lower energy. This is the mechanism through which heat conduction occurs. The stiffer the atomic bonds and the more regular the lattice

structure, the more easily energy is transferred between atoms through these vibrations. A second mechanism for conducting heat occurs in metallic materials, because they contain free electrons which can travel through the lattice, colliding with other particles and re-distributing energy in the process. The presence of these free electrons explains why metals are such good thermal conductors - they benefit

from the combined effect of the movement of free electrons and vibrations of the atomic lattice. In gases and liquids conduction occurs mostly through collisions of atoms and molecules. In the study of conduction we're usually interested in determining the heat transfer rate, which is the amount of energy that flows through a defined area of an object