When difference in temperature exists between two bodies, heat flows from higher temperature body to low temperature body. This process is known as “heat transfer”.
Types of heat transfer
The heat transfer within a solid substance or between solid substances in contact with each other from high temperature region to low temperature region is called as conduction.
The heat transfer from a hot solid body to a comparatively cool liquid or heat transfer between two liquids at different temperature when brought in contact of each other is called as convection.
For eg : When a vessel containing water is heated the vessel gets heated first via conduction, then the water inside it gradually starts heating up from bottom to top, this heating of water is called as convection heating.
When heat transfer takes place in the form of electromagnetic radiation then the mode of transfer is said to be radiation. In radiation no medium is required for heat transfer.
For eg : The sun is extremely hot, however there isn’t any medium between the sun and the earth, still we feel its warmth. This is due to radiation