Question

As a rough approximation, the human body may be considered to be a cylinder of length l=2.0m and circumference c=0.8m . (to simplify things, ignore the circular top and bottom of the cylinder, and just consider the cylindrical sides.) if the emissivity of skin is taken to be e=0.6 , and the surface temperature is taken to be t= 30 ∘ c , how much thermal power p does the human body radiate?

Answer 1

e= 0.6
Constant sigma is 5.6704004× 10∧ (-8)
The area is LC = 2× .8 = 1.6m∧2
to convert degrees celcious to Kelvin =303K
The equation is 
P = e ? AT∧4.
Then the answer is 460 watts.

Answer 2

Answer:

458.826 watts

Explanation:

According to Stefan-Boltzmann's Law, thermal energy emitted by a black body per second per unit area is directly proportional to the fourth power of the absolute temperature and is given by;

$\frac{P}{A}$ = σ$eT^{4}$

P = ?

A = l x c = 2 x 0.8 = $1.6m^{2}$

(Please ignore Armstrong symbol, I don't know how it appeared using the equation tool)

σ = $5.6703 X 10^{-8}  watt/m^{2} K^{4}$

e = 0.6

T = $30^{o} C$ = 303 K

P = σeTA

P = $5.6703 X 10^{-8}$ x 0.6 x $303^{4}$ x 1.6

P = 458.826 watts