Physics - Heat & Thermo Question with Solution | TestHub

Thermal resistance ($R_{th}$) for a material is defined as $R_{th}=\frac{L}{KA}$, where $L$ is length, $K$ is thermal conductivity, and $A$ is cross-sectional area.

When two rods are joined end to end, they are in series. For series combination, the equivalent thermal resistance is the sum of individual thermal resistances. So, $R_{eq}=R_{th,c}+R_{th,s}=\frac{L_c}{K_c{A}_c}+\frac{L_s}{K_s{A}_s}$.