A spherical ball A of surface area 20 is kept at the cantre of a hollow spherical shell B of area . The surface of A & the inner surface of B emit as blackbodies. assume that the thermal conductivity of B IS POOR &  that of A is high & there is vacuum between A&B. the heat capacities of A & B are 42J per *C & 82J per*C. Initially the temp of A is 100*C & that of B is 20*C. find the rate of change of temp of A &  that of B @ this instant.

is the mass of the shell n the ball given?

is the answer...........

0.023*C/sec for A

0.0192*C/sec for B

Apply Stefan Boltamzn Law to solve this problem, according to which

The energy of thermal radiation emitted per unit time by a blackbody of surface area A is given by

u = sigma*A*T⁴

Here sigma is a universal constant known as Stefan boltzmann constant and T is the temperarute

Sigma = 5.67 x 10^-8 W/m²-K⁴