Question

A body of surface area 15 x 10^-3 m² emits 0.4 kcal in 20 second at a temperature 70° C. The emissive power of the surface at that temperature is ____________.

Options

• 1.3 kcal/m² s

• 5.6 x 10^-3 kcal/m² s

• 0.5 kcal/m² s

• 2.7 x 10^-3 kcal/m² s

Answer 1

A body of surface area 15 x 10^-3 m² emits 0.4 kcal in 20 second at a temperature 70° C. The emissive power of the surface at that temperature is 1.3 kcal/m² s.

Explanation:

`"R" = "Q"/"At"`

` = 0.4/(15 xx 10^-3 xx 20)`

` = 1.3  "kcal/""m"^2 "s"`