what is convetion

Convection is the process of heat transfer in fluids by the actual motion of matter. It occurs in liquids and gases and may be natural or forced. Convection involves the bulk movement of molecules within fluids such as gases and liquids. The initial heat transfer between the object and the fluid takes place through conduction, but the bulk heat transfer happens due to the motion of the fluid. Convection creates uneven heating and cooling that causes movement of the substance, which is called a convection current. Convection currents can be set up by local heating effects such as solar radiation or contact with cold surface masses. Atmospheric convection currents primarily move vertically and account for many atmospheric phenomena, such as clouds and thunderstorms. Convection is the rising motion of warmer areas of a liquid or gas, and the sinking motion of cooler areas of liquid or gas, sometimes forming a complete cycle.