Convection occurs in which kind of medium?

• A. Gases
• B. Fluids
• C. Solids
• D. Vacuum

Answer: (B)

Convection is heat transfer by the bulk motion of a substance that can flow. For convection to occur, the medium must be able to move as a whole; solids don’t flow like liquids or gases, so heat in solids is mainly transferred by conduction. Vacuum has no medium at all, so convection cannot happen there. Among the options, fluids best fits because it includes both liquids and gases—the substances that can circulate and form convection currents. Gases alone would be correct too, but fluids is the broader, more complete category that covers all convecting media. Examples include warm air rising in a room or boiling water where the liquid circulates to transport heat.