A sphere of density `d`, specific heat `s` 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. If the temperature difference is `DeltaT` and surrounding temperature is `T_(0)` then rate of fall in temperature will be
[Given that `DeltaT lt lt T_(0)`]

Options

A. `(4 sigma T_(0)^(3) DeltaT)/(rdc)`
B. `(12 sigma T_(0)^(3) DeltaT)/(rdc)`
C. `(12 sigma T_(0)^(4) DeltaT)/(rdc)`
D. `(12 sigma Delta T)/(rdc T_(0)^(3))`

Answer

B