A black body with surface area 0.001 m2 is heated up to a temperature 400 K and is suspended in a room temperature 300 K .The initial rate of loss of heat from the body to room is

The rate of heat emission,  u=σAT4At room temperature, the rate of absorption is  u0=σAT04The net rate of heat loss, u−u0=σAT4−T04Given,  A=0.001m2T=400K and T0=300KThus,  u−u0=5.67×10−8×0.001×(400)4−(300)4=0.99W≈1W