Which principle states that heat is created in one place and carried to another by means of air or water?

• A. Conduction principle
• B. Convection principle
• C. Radiation principle
• D. Heat-transfer principle

Answer: (D)

Convection is the mechanism by which heat is carried by moving air or water. When a fluid (like air or water) moves, it transports thermal energy from warmer areas to cooler ones as the fluid itself circulates. This is different from conduction, which transfers heat through direct contact or stationary fluids by molecular interactions, and from radiation, which transfers heat via electromagnetic waves without needing a medium. The idea of a simple “heat-transfer principle” isn’t a standard description of how heat moves, so it doesn’t fit. Examples include warm room air rising and circulating after a heater, or heated water in a pot moving as it boils, spreading heat throughout.