Which heat transfer mechanism involves the movement of heated fluid causing energy redistribution?

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

Answer: (B)

Convection is the mechanism where heated fluid moves and carries energy with it, redistributing heat through the substance. When fluid is heated, it becomes less dense and rises, while cooler, denser fluid sinks to take its place, creating a circulating flow. This bulk movement of fluid transports thermal energy from warmer regions to cooler ones, which is why convection is so effective in air and water.

Conduction, by contrast, transfers energy through direct contact and microscopic interactions without large-scale fluid movement. Radiation transfers heat via electromagnetic waves and can occur without any medium. Osmosis isn’t a heat-transfer process at all; it’s the movement of solvent across a semipermeable membrane driven by concentration differences.