The transfer of heat to circulating air, such as when cool air moves across the body's surface, is called which term?

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

Answer: (A)

Convection is heat transfer by the movement of a fluid, in this case air, past a surface. When cool air moves across the body's surface, it carries heat away as it flows, cooling the body more efficiently than if the air were still. This moving-air heat loss is different from conduction, which requires direct contact with a solid, and from radiation, which transfers heat as infrared energy without contact, and from evaporation, which cools by changing sweat to vapor. In practice, convection explains why wind or a fan can accelerate cooling in cold environments and why drafts can feel chilling to someone exposed to the elements.