Which heat transfer mode can operate without any physical medium between source and destination?

Which heat transfer mode can operate without any physical medium between source and destination?

• A. Conduction
• B. Convection
• C. Radiation
• D. Thermal resistance

Answer: (C)

Radiation can transfer heat without any physical medium between source and destination. It moves energy through electromagnetic waves, so it can travel through vacuum or empty space. This is why the Sun heats the Earth despite the vast space between them. Conduction requires direct contact or interaction between particles within a solid or between solids and liquids, transferring energy through molecular collisions and vibrations. Convection needs a moving fluid—gas or liquid—to carry heat as it flows. Thermal resistance isn’t a distinct mode of heat transfer; it’s a way to describe how hard it is for heat to move through a material or across an interface.

Radiation can transfer heat without any physical medium between source and destination. It moves energy through electromagnetic waves, so it can travel through vacuum or empty space. This is why the Sun heats the Earth despite the vast space between them.

Conduction requires direct contact or interaction between particles within a solid or between solids and liquids, transferring energy through molecular collisions and vibrations. Convection needs a moving fluid—gas or liquid—to carry heat as it flows. Thermal resistance isn’t a distinct mode of heat transfer; it’s a way to describe how hard it is for heat to move through a material or across an interface.