How is the thermal conductivity (k) measured?

Thermal conductivity (k) is a measure of a material's ability to conduct heat. It is defined by the formula as the rate of heat transfer through a material per unit area per unit temperature difference. The correct formula for thermal conductivity is indeed given as Q divided by the product of area (A) and the temperature difference (ΔT).

In this formulation, Q represents the amount of heat transfer (in watts or joules), A is the cross-sectional area through which the heat is being transferred, and ΔT is the temperature difference across the material (in degrees Celsius or Kelvin). This relationship shows that thermal conductivity increases with greater heat transfer and a smaller area or temperature difference, effectively illustrating how heat flows through the material.

To understand why this is the correct measure, consider that the result provides a clear, standardized way to evaluate how well different materials conduct heat — critical for various applications in HVAC and insulation work. High thermal conductivity means a material is efficient at transferring heat, which is essential in designing heating and cooling systems.