The circulation of the oil by heat is called ________.

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

Answer: (B)

Convection is heat transfer by the circulation of a fluid. When oil is heated, the portion near the heat source becomes less dense and rises, while cooler oil moves in to take its place and sinks. This creates a continuous looping motion that carries heat through the liquid.

Conduction would involve energy transfer through contact or molecular interactions without bulk movement of the oil. Radiation is heat transfer by electromagnetic waves, not by moving the liquid. Evaporation is a phase change from liquid to vapor, not a mode of transferring heat via circulating fluid.