Which describes convection?

• A. Heat transfer through a fluid causing currents as warm fluid rises.
• B. Heat transfer through vacuum via waves.
• C. Heat transfer by direct contact in solids.
• D. Not a mode of heat transfer.

Answer: (A)

Convection is heat transfer by the movement of a fluid. When part of a fluid is heated, it becomes lighter and rises, while cooler, denser fluid sinks, setting up a circulating current that carries warmth with it. That’s exactly what the statement describes: heat transfer through a fluid causing currents as warm fluid rises. In contrast, heat transfer through a vacuum happens by radiation, not convection, because there are no particles to move. Heat transfer by direct contact in solids is conduction, where energy moves through touching particles, not by fluid motion. Saying there’s no mode of heat transfer isn’t correct because convection is a real mode of heat transfer.