Which statement correctly defines convection?

Which statement correctly defines convection?

• A. Convection is transfer of heat through currents caused by difference in temperature, which cause difference in density (liquids and gases)
• B. Heat transfer by electromagnetic waves
• C. Heat transfer through direct contact
• D. Cooling by evaporation

Answer: (B)

Convection is heat transfer through the movement of a fluid, driven by temperature differences that change the fluid’s density. When part of a fluid gets warmer, it becomes lighter and rises, while cooler, denser fluid sinks to take its place. This creates circulating currents that transport heat, as seen in warm air rising in a room or water boiling in a pot where loops of motion form. This is different from radiation, which transfers heat via electromagnetic waves, without any physical medium moving. It’s also distinct from conduction, which happens through direct contact between substances, and from evaporation-related cooling, which involves a phase change.

Convection is heat transfer through the movement of a fluid, driven by temperature differences that change the fluid’s density. When part of a fluid gets warmer, it becomes lighter and rises, while cooler, denser fluid sinks to take its place. This creates circulating currents that transport heat, as seen in warm air rising in a room or water boiling in a pot where loops of motion form.

This is different from radiation, which transfers heat via electromagnetic waves, without any physical medium moving. It’s also distinct from conduction, which happens through direct contact between substances, and from evaporation-related cooling, which involves a phase change.