Answer :
Heat transfer in liquids and gases takes place primarily by convection. Convection is the transfer of heat through the movement of the medium itself, such as the movement of air or water. When a liquid or gas is heated, it becomes less dense and rises, displacing cooler, denser fluid which then sinks and gets heated, creating a continuous circulation of fluid. This process effectively transfers heat throughout the medium. Convection is the dominant mode of heat transfer in fluids because of the mobility of the particles.
While conduction also occurs in liquids and gases, it is less efficient compared to convection. Conduction is the transfer of heat through a material without any movement of the material itself. In liquids and gases, molecules are further apart compared to solids, making conduction less effective due to fewer collisions between molecules. Radiation, on the other hand, is the transfer of heat through electromagnetic waves and does not require a medium. While radiation can occur in liquids and gases, it is often less significant compared to convection and conduction.
Therefore, the correct answer is (B) Convection, as it is the primary mode of heat transfer in liquids and gases. Conduction also plays a role, but it is less significant due to the nature of the fluid medium. Radiation can occur but is usually less important in these contexts.
Here is the complete question:
"Heat transfer in liquids and gases takes place by....
(A) Conduction
(B) Convection
(C) Radiation
(D) Conduction and Radiation"
