Final answer:
The unit for thermal conductivity is watts per meter per Kelvin (W/m·K) or joules per second per meter per Kelvin (J/s·m·K), representing the rate of heat transfer through a material per unit temperature gradient.
Step-by-step explanation:
The unit for thermal conductivity is expressed in terms of the rate at which heat passes through a specified material, exemplified by the symbol ‘k’. Given the equation Q/t = kA(T₂ - T₁)/d, where ‘Q/t’ is the rate of heat transfer in watts (W) or joules per second (J/s), ‘A’ is the surface area, and ‘d’ is the thickness of the material, the correct unit for thermal conductivity is watts per meter per Kelvin (W/m·K) or joules per second per meter per Kelvin (J/s·m·K). This unit accounts for the energy transfer rate (in watts or joules per second), the distance heat travels (in meters), and the temperature difference (in Kelvin).