What is a mode of heat transfer that does not require physical contact between the warmer substance and the cooler substance?

What is a mode of heat transfer that does not require physical contact between the warmer substance and the cooler substance?

• A. Conduction
• B. Convection
• C. Radiation
• D. Insulation

Answer: (C)

Radiation is the correct answer because it is a mode of heat transfer that occurs through electromagnetic waves, allowing heat to be transmitted even through a vacuum. Unlike conduction, which relies on direct contact between materials for heat to transfer, and convection, which requires a fluid (liquid or gas) to carry heat through movement, radiation can occur across empty spaces without any medium. For example, the heat from the sun reaching the Earth travels through the vacuum of space by radiation. Insulation, while related to heat transfer, does not describe a mode of heat transfer itself; rather, it refers to materials or methods that reduce the flow of heat between two areas, which is a different concept.

Radiation is the correct answer because it is a mode of heat transfer that occurs through electromagnetic waves, allowing heat to be transmitted even through a vacuum. Unlike conduction, which relies on direct contact between materials for heat to transfer, and convection, which requires a fluid (liquid or gas) to carry heat through movement, radiation can occur across empty spaces without any medium. For example, the heat from the sun reaching the Earth travels through the vacuum of space by radiation.

Insulation, while related to heat transfer, does not describe a mode of heat transfer itself; rather, it refers to materials or methods that reduce the flow of heat between two areas, which is a different concept.