First slide

Radiation

Question

A sphere of density p, specific heat capacity c and radius r is hung by a thermally insulating thread in an enclosure which is kept at a lower temperature than the sphere. The temperature of the sphere starts to drop at a rate which depends upon the temperature difference between the sphere and the enclosure and the nature of the surface of sphere and is proportional to:

Moderate

A

$\frac{c}{r^{3} ρ}$
B

$\frac{1}{r^{3} ρc}$
C

3r³pc
D

$\frac{1}{rpc}$

Solution

$[\frac{- dT}{dt}] = \frac{σ A}{mc} [T - T_{0}]$
$= \frac{σ 4 {πr}^{2}}{ρ \times \frac{4}{3} {πr}^{3} c} [T - T_{0}]$
$∴ [\frac{- dT}{dt}] \propto \frac{1}{ρrc}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App