How does natural convection occur?

Natural convection occurs due to differences in density created by temperature variations within a fluid. When a fluid is heated, its temperature increases, causing the fluid to expand and become less dense. This decrease in density allows the warmer, lighter fluid to rise, while the cooler, denser fluid sinks. This movement establishes a circulation pattern, or convection current, that transfers heat throughout the fluid.

In contrast to this process, actively stirring the fluid introduces forced convection, where external energy is applied, rather than relying on density differences. Similarly, external mechanical forces would lead to fluid movement that is distinct from the natural convection process. Lastly, when fluids are isolated from any movement, there would be no mechanism for heat transfer through convection, as the lack of density variation movement prevents circulation. Hence, the correct understanding of natural convection focuses entirely on the effects of temperature-induced density changes leading to fluid movement.