Conduction is the redistribution of thermal energy that occurs in a solid body due to differences in temperature. It’s one of three modes of heat transfer, along with convection and radiation.

Conductive heat transfer can be described by Fourier’s Law. It states that the rate of heat transfer between two points is proportional to the area of through which the heat transfer occurs, to the difference in temperature between the two points, and to a material constant called thermal conductivity.

Fourier’s law can only be applied if the temperature gradient is known, which requires the distribution of temperature within the body to be known. The temperature distribution in a body can be determined by solving the heat equation – a partial differential equation that describes how heat will flow throughout an object.

These topics – conduction, Fourier’s Law, thermal conductivity and the heat equation – are covered in detail in the animated video below.

Any object that has a temperature greater than absolute zero is constantly emitting electromagnetic waves that travel through space at the speed of light. These electromagnetic waves that produce thermal radiation, one of three ways in which heat transfer can occur between different objects, along with conduction and convection.

The video below explores thermal radiation in detail. It starts by covering electromagnetic waves, the Stefan-Boltzmann law, black bodies and emissive power.

It then covers emissivity, absorptivity, transmissivity and reflectivity, as well as view factors, all key concepts for being able to calculate the radiative heat transfer between two objects.