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
- [AIEEE 2005]
- A
$\frac{{{r_1}\,{r_2}}}{{({r_1} - {r_2})}}$
- B
$({r_2} - {r_1})$
- C
$({r_2} - {r_1})({r_1}\,{r_2})$
- D
$In \left( {\frac{{{r_2}}}{{{r_1}}}} \right)$
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- [AIPMT 2010]
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$Assertion :$ Woolen clothes keep the body warm in winter
$Reason :$ Air is a bad conductor of heat.
$Assertion :$ Woolen clothes keep the body warm in winter
$Reason :$ Air is a bad conductor of heat.
- [AIIMS 2002]