Question

Which mode of heat transfer is dominant in vacuum?

• A. Conduction
• B. Convection
• C. Radiation
• D. All are equal

Hint:

Radiation follows the Stefan-Boltzmann Law: \( Q = \sigma A T^4 \).
Notice that heat transfer by radiation is highly dependent on the absolute temperature (raised to the power of 4).

Answer 1

The Correct Option is C

To determine which mode of heat transfer is dominant in a vacuum, we need to understand the characteristics of the different modes of heat transfer: conduction, convection, and radiation.

1. Conduction: Conduction is the transfer of heat through a solid or between solids in direct contact. It requires a material medium to transfer heat from one molecule to another. Since a vacuum lacks any material medium, conduction cannot occur in a vacuum.
2. Convection: Convection involves the transfer of heat by the motion of fluids (liquids or gases). It occurs due to the movement of molecules within fluids. Since there are no fluids in a vacuum, convection also cannot occur.
3. Radiation: Radiation is the transfer of heat energy through electromagnetic waves. It does not require any medium and can occur through empty space. This is how the Sun's heat reaches the Earth through the vacuum of space.

Given these explanations, radiation is the dominant mode of heat transfer in a vacuum, as it does not require a material medium to transmit heat.

Correct Answer: Radiation