The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperatures $T_1$ and $T_2$, respectively. The radial rate of flow of heat in a substance between the two concentric spheres, is proportional to
The figure shows a system of two concentric spheres of radii $r_1$ and $r_2$ and kept at temperatures $T_1$ and $T_2$, respectively. The radial rate of flow of heat in a substance between the two concentric spheres, is proportional to
- A
$\frac{{\left( {{r_2} - {r_1}} \right)}}{{\left( {{r_1}{r_2}} \right)}}$
- B
$\ln \left( {\frac{{{r_2}}}{{{r_1}}}} \right)$
- C
$\frac{{\left( {{r_1}{r_2}} \right)}}{{\left( {{r_2} - {r_1}} \right)}}$
- D
$\left( {{r_2} - {r_1}} \right)$
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