Question

The emissive power of a sphere of area 0.02 m² is 0.5 kcal s^-1 m^-2. What is the amount of heat radiated by the spherical surface in 20 second?

Answer 1

Given : R = 0.5 kcal-s^-1 'm^-2 , A =0.02 m², t=20s

Q = RAt = (0.5) (0.02) (20) = 0.2 kcal

0.2 kcal is the required quantity.