Question

A hollow and a solid sphere of same material and identical outer surface under identical condition are heated to the same temperature at the same time (both have same $e, a$) :

• A. In the beginning both will emit equal amount of radiation per unit time
• B. In the beginning both will absorb equal amount of radiation per unit time
• C. Both spheres will have same rate of fall of temperature (dT/dt)
• D. Both spheres will have equal temperatures at any moment

Answer 1

Answer: (A), (B)

As initially they are at same temperature their radiation rates will be equal and their absorption rate from surrounding will also be equal but as time passes, due to the difference in masses of the two their temperature will differ and rates will also be changed at later instants and due to this rate of fall of temperatures will also be different at later instants.