Fourier's Law expresses the conduction heat transfer rate as qx = -k A (dT/dx). Which quantity is the material's insulating property in this law?

Fourier's Law expresses the conduction heat transfer rate as qx = -k A (dT/dx). Which quantity is the material's insulating property in this law?

• A. k
• B. h
• C. ε
• D. σ

Answer: (A)

In conduction, how readily heat moves through a material is described by its thermal conductivity, k. In Fourier’s Law, the term -k A (dT/dx) shows that the heat transfer rate scales with k: a larger k means heat flows more easily (a better conductor), while a smaller k means heat is resisted more (a better insulator). The other symbols correspond to different heat transfer modes or properties: h is the convective heat transfer coefficient, ε is emissivity for radiation, and σ is the Stefan-Boltzmann constant used in radiative transfer.

In conduction, how readily heat moves through a material is described by its thermal conductivity, k. In Fourier’s Law, the term -k A (dT/dx) shows that the heat transfer rate scales with k: a larger k means heat flows more easily (a better conductor), while a smaller k means heat is resisted more (a better insulator). The other symbols correspond to different heat transfer modes or properties: h is the convective heat transfer coefficient, ε is emissivity for radiation, and σ is the Stefan-Boltzmann constant used in radiative transfer.