The heat transfer by conduction through a thick sphere is given by
A. $${\text{Q}} = \frac{{2\pi {\text{k}}{{\text{r}}_1}{{\text{r}}_2}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{{{\text{r}}_2} - {{\text{r}}_1}}}$$
B. $${\text{Q}} = \frac{{4\pi {\text{k}}{{\text{r}}_1}{{\text{r}}_2}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{{{\text{r}}_2} - {{\text{r}}_1}}}$$
C. $${\text{Q}} = \frac{{6\pi {\text{k}}{{\text{r}}_1}{{\text{r}}_2}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{{{\text{r}}_2} - {{\text{r}}_1}}}$$
D. $${\text{Q}} = \frac{{8\pi {\text{k}}{{\text{r}}_1}{{\text{r}}_2}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{{{\text{r}}_2} - {{\text{r}}_1}}}$$
Answer: Option B
Solution (By Examveda Team)
The heat transfer by conduction through a thick sphere is given by $${\text{Q}} = \frac{{4\pi {\text{k}}{{\text{r}}_1}{{\text{r}}_2}\left( {{{\text{T}}_1} - {{\text{T}}_2}} \right)}}{{{{\text{r}}_2} - {{\text{r}}_1}}}.$$This Question Belongs to Mechanical Engineering >> Heat And Mass Transfer
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