Which statement about convection is NOT true?

Which statement about convection is NOT true?

• A. It requires a circulating medium.
• B. It can occur in liquids and gases.
• C. It relies on direct contact of solids.
• D. It involves movement of the fluid to transfer heat.

Answer: (C)

Convection transfers heat through the bulk movement of a fluid. This requires a circulating medium that can move, and it can occur in both liquids and gases. The heat is carried as the fluid moves, whether by natural circulation (hot fluid rising) or forced circulation (fans or pumps). The statement that relies on direct contact of solids is not true for convection; that describes conduction, where heat is transferred through solids or between surfaces in contact. So the remaining true descriptions are that convection needs a circulating medium, can happen in liquids and gases, and involves the movement of the fluid to transfer heat.

Convection transfers heat through the bulk movement of a fluid. This requires a circulating medium that can move, and it can occur in both liquids and gases. The heat is carried as the fluid moves, whether by natural circulation (hot fluid rising) or forced circulation (fans or pumps). The statement that relies on direct contact of solids is not true for convection; that describes conduction, where heat is transferred through solids or between surfaces in contact. So the remaining true descriptions are that convection needs a circulating medium, can happen in liquids and gases, and involves the movement of the fluid to transfer heat.