Net rate of heat transfer by radiation

Definition

The net rate of heat transfer by radiation is the difference between the amount of thermal radiation emitted by a body and the amount absorbed from its surroundings. It depends on factors such as temperature, surface area, and emissivity.

5 Must Know Facts For Your Next Test

1. The formula for the net rate of heat transfer by radiation is given by $Q_{net} = \sigma A (T_1^4 - T_2^4)$, where $\sigma$ is the Stefan-Boltzmann constant, $A$ is the surface area, and $T_1$ and $T_2$ are the temperatures of the object and its surroundings in Kelvin.
2. Emissivity ($\epsilon$) ranges from 0 to 1 and indicates how efficiently a surface emits thermal radiation compared to a perfect blackbody.
3. A higher temperature difference between an object and its surroundings increases the net rate of heat transfer by radiation.
4. Surfaces with high emissivity radiate more heat compared to surfaces with low emissivity.
5. Net heat transfer by radiation does not require a medium; it can occur through a vacuum.

Review Questions

Related terms

Stefan-Boltzmann Law: States that the power radiated per unit area of a blackbody is proportional to the fourth power of its absolute temperature: $P = \sigma T^4$.

Emissivity:

A measure of how effectively a surface emits thermal radiation compared to a perfect blackbody; ranges from 0 to 1.

Blackbody:

An idealized physical body that absorbs all incident electromagnetic radiation regardless of wavelength or angle.