What is convection?

• A. Conduction
• B. Convection
• C. Radiation
• D. Evaporation

Answer: (B)

Convection is heat transfer through the bulk movement of a fluid, such as air or blood. When part of the fluid is heated, it becomes less dense and rises, while cooler, denser portions sink, creating a circulating current that carries heat with it. This is why warm air rises and why blood flow can move heat from the body's core toward the skin. In clinical settings, devices that blow warm or cool air over a patient rely on convection to transfer heat efficiently. In contrast, conduction is heat transfer by direct contact between solids, radiation transfers energy through space via electromagnetic waves, and evaporation cools a surface as liquid turns into vapor.