Discuss briefly natural and forced convection.
Convection is a part of both processes. Convection is a form of heat transfer within fluid substances. Convection occurs due to temperature and density differences. As particles gain heat energy, they expand. Thus, the heated particles have greater volume and lower density. This causes the heated particles to rise. Oppositely, as particles lose energy, they contract and come closer to one another. Thus, as the particles lose heat, volume decrease and density increases. This causes the particles that have lost heat to sink. The rising of heated particles and sinking of cooler particles forms a cycle that is known as a convection current.
The energy source is different for forced and natural convection. An external force, such as a pump or fan, is the source of energy that causes the fluid movement of forced convection. Natural convection is not supplied by an external force. The fluid movement of natural convention results from the natural heating and cooling of the fluid. An example of a natural convection current would be the magma that is housed below the mantel. The magma is heated by the natural heat supplied by the Earth’s core.