What are the units of thermal conductivity?

The units of thermal conductivity are watts per metre per kelvin (W/m·K).

Thermal conductivity is a measure of a material's ability to conduct heat. It tells us how easily heat can pass through a material. The unit "watts per metre per kelvin" (W/m·K) breaks down into three parts: watts (W), metres (m), and kelvin (K).

Watts (W) measure the rate of heat transfer. One watt is equivalent to one joule of energy transferred per second. When we talk about thermal conductivity, we are interested in how much heat energy is transferred through a material over time.

Metres (m) refer to the thickness of the material. If you have a thicker piece of material, it will generally conduct heat less efficiently than a thinner piece of the same material. This is because the heat has to travel a longer distance.

Kelvin (K) is the unit of temperature difference. Thermal conductivity depends on the temperature difference between the two sides of the material. A larger temperature difference usually means more heat will be transferred.

So, when we say a material has a thermal conductivity of, for example, 0.5 W/m·K, it means that for every metre of thickness, and for every degree of temperature difference in kelvin, 0.5 watts of heat energy will be transferred through the material.

Understanding thermal conductivity is important in many real-world applications, such as building insulation, designing heat sinks for electronics, and even in clothing materials to keep us warm or cool. By knowing the thermal conductivity of different materials, we can make better choices to manage heat effectively.