Forced-air furnaces primarily function using which method of heat transfer?

Forced-air furnaces primarily function through convection, which is the process of heat transfer that occurs in fluids (liquids and gases) due to the movement of the fluid itself. In a forced-air furnace system, the furnace heats the air, and then a blower circulates this warm air throughout the space, creating a temperature difference that promotes the flow of heated air into living areas.

This method is particularly efficient for heating spaces quickly because it continuously moves heated air, allowing for even distribution of warmth. As the warm air rises, it displaces cooler air, creating a cycle that maintains comfort within the space.

Conduction involves heat transfer through direct contact, radiation is the transfer of heat in the form of electromagnetic waves, and evaporation refers to the process where liquid turns into vapor, none of which are the primary means by which forced-air systems operate. Thus, convection is the correct answer in the context of how forced-air furnaces operate and distribute heat effectively.