The heat transfer by conduction through a thick cylinder (Q) is given by (where T1 = Higher temperature, T2 = Lower temperature, r1 = Inside radius, r2 = Outside radius, l = Length of cylinder and k = Thermal conductivity)

Answer: Option A

The heat transfer by conduction through a thick cylinder (Q) is given by
$$\text{Q}=\frac{2\pi l\text{k}\left({\text{T}}_1-{\text{T}}_2\right)}{2.3\log \left(\frac{{\text{r}}_2}{{\text{r}}_1}\right)}$$
Where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, $$l$$ = Length of cylinder and k = Thermal conductivity.