Which process is heat transfer via moving fluids?

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

Answer: (B)

Convection is heat transfer through moving fluids. When a fluid such as air or water moves, it carries thermal energy with it from warmer areas to cooler ones. Heating causes the fluid to become less dense and rise, while cooler, denser fluid sinks, creating a circulating flow that transports heat throughout the space or system. This is different from conduction, which spreads heat through direct contact and molecular interaction without bulk fluid movement, and from radiation, which transfers energy via electromagnetic waves and can occur even in a vacuum. Evaporation involves a phase change with latent heat but isn’t the mechanism of heat transfer by moving fluid.