Which statement about convection is true?

Which statement about convection is true?

• A. It transfers heat mainly through direct contact of solids.
• B. It uses electromagnetic radiation to transfer heat.
• C. It involves the movement of a liquid or gas to transfer heat.
• D. It occurs only in vacuum.

Answer: (C)

Convection is heat transfer caused by the movement of a fluid. When a liquid or gas is heated, it becomes less dense and tends to rise, while cooler fluid sinks, creating a circulating current that carries heat with it. This can happen naturally, as warm air rising from a heater, or can be driven by devices like fans or pumps. This is different from conduction, which transfers heat through direct contact between solids, and from radiation, which uses electromagnetic waves to transfer heat. Convection also cannot occur in a vacuum, because there’s no fluid to move.

Convection is heat transfer caused by the movement of a fluid. When a liquid or gas is heated, it becomes less dense and tends to rise, while cooler fluid sinks, creating a circulating current that carries heat with it. This can happen naturally, as warm air rising from a heater, or can be driven by devices like fans or pumps.

This is different from conduction, which transfers heat through direct contact between solids, and from radiation, which uses electromagnetic waves to transfer heat. Convection also cannot occur in a vacuum, because there’s no fluid to move.