Question

Heat transfer by convection occurs in:

• A. Solids
• B. Solids and liquids
• C. Solid surface to liquids and gases
• D. Gases

Hint:

Convection requires a fluid medium (either liquid or gas) to facilitate the transfer of heat through the movement of particles. Solids rely on conduction for heat transfer, which involves no fluid motion.

Answer 1

The Correct Option is C

Convection is a process of heat transfer that involves the bulk movement of a fluid, which can be a liquid or gas. In this process, the heated molecules in the fluid move away from the heat source, transferring the heat energy to cooler regions. This movement of fluid particles is a key characteristic of convection.
In solids, however, heat is transferred through conduction, where thermal energy is passed from particle to particle without bulk motion of the material. This is because solids have tightly packed molecules, and the heat transfer occurs via vibrational energy from one molecule to the next. Hence, convection does not occur in solids.
The correct mechanism for convection occurs at the interface between a solid and a fluid (liquid or gas). For example, when a metal pan is heated on a stove, heat is transferred from the pan's surface (solid) to the surrounding air (gas) or any liquid in contact with it. The heated fluid then moves, carrying the heat away from the surface.
Thus, the correct answer is option (3): heat transfer by convection occurs between a solid surface and the fluids (liquids and gases) in contact with it.