Question
A solid sphere of radius R, made from a material of density ρ and specific heat s is heated to temperature T and placed in an enclosure at temperature T0 Show that the:
(i) rate of loss of heat varies directly with square of radius and independent of specific heat and density of the material,
(ii) rate of cooling varies inversely with radius, specific heat and density.
Solution
i) According to Stefan’s law, the rate of loss of heat by a body is, 
From the above relation, it is clear that the rate of loss of heat varies directly with the square of radius and independent of specific heat of material and density of material.
ii) Now, the rate of cooling varies inversely with radius, specific heat, and density. 
Hence, the result.
