Which one of the following is the SI unit of the thermal conductivity of a material?

Thermal conductivity is a physical property that measures a material's ability to transfer heat [1]. It is defined as the amount of heat energy flowing through a unit area of material per unit time under a unit temperature gradient [1]. Mathematically, it is derived from Fourier's Law, where the heat flow rate (measured in Watts) is proportional to the temperature gradient (Kelvin per meter) and the cross-sectional area (square meters) [2]. Consequently, the SI unit is expressed as Watts per meter-Kelvin, which is written as W/(m·K) or W m⁻¹ K⁻¹ [2]. While alternative units like J s⁻¹ m⁻¹ K⁻¹ are physically equivalent because 1 Watt equals 1 Joule per second, the standard SI representation used in scientific literature and engineering is W m⁻¹ K⁻¹ [2]. Option 1 correctly represents this standard notation.

Sources

1. [1] https://sathee.iitk.ac.in/article/physics/thermal-conductivity-unit/
2. [2] https://en.wikipedia.org/wiki/List_of_thermal_conductivities