Question

a person with external body temperature 35 degree celsius is present in a room at temperature 25 degree Celsius assuming the emissivity of the body of the person to be 0.5 and surface area of the body of the person is 2.0 m square calculate the radiant power of the person

Answer 1

The person radiates energy at a rate:
 
P = Q / ∆t =A[(T1)^4 - (T2)^4] , T1>T2

here, P is the radiant power of the person,
  = 0.5 emissivity of the body of the person,
  = 5.672 x10^-8 J/(s.m^2.K^4) is the Stefan – Boltzmann constant,
  = 2.0m^2 is the surface area of the body of the person
 and 
T1 is the temperature of the person = 35+273 =308K
and T2 is the temperature of the surroundings = 25+273  =298K

Then, the radiant power of the person will be:

P = A[(T1)^4 - (T2)^4]
P = 0.5 x 5.672 x 10^-8 x 2 x[(308)^4 - (298)^4]
P = 5.672 x 10^-8 x 1113028080
P = 6313095269.76 x 10^-8
P = 63.13 W