The figure shows a system of two concentric spheres of radii `r_1 and r_2` are kept at temperature `T_1 and T_2`, respectively. The radial rate of flow of heat in a substance between the two concentric spheres is proportional to

Options

A. `(r_(1)r_(2))/(r_(2)-r_(1))`
B. `(r_(2)-r_(1))`
C. `((r_(2)-r_(1)))/(r_(1)r_(2))`
D. `log_(e)((r_(2))/(r_(1)))`

Answer

A

Explanation

`H=-k4pir^(2)(dT)/(dr)impliesHprop(r_(1)r_(2))/(r_(2)-r_(1))`