Suppose the skin temperature of a naked person is 34°C when the person is standing inside a room whose temperature is 25°C. The skin area of the individual is 2.0 m2
a) Assuming the emissivity is 0.80, find the net loss of radiant power from the body
b) Determine the number of food Calories of energy (1 food Calorie = 4186 J) that is lost in one hour due to the net loss rate obtained in part (a). Metabolic conversion of food into energy replaces this loss.
I used
a)
Q/t = emissivity x stefan-boltzmann constant x T^4 x A
= 0.8 X 5.67^-8 X 298.15^4 X 2
=719.277
b) 1 watt per hour = 3600J
total joules = 3600 X 719.277 = 2589399.087
2589399.087 /4186 = total calories
Answers are wrong
To calculate the net loss of radiant power from the body, we can use the Stefan-Boltzmann law:
a) The equation to calculate the net loss of radiant power is given by:
Q/t = ε * σ * (T^4 - T_room^4) * A
where:
Q/t is the net loss of radiant power (in Watts),
ε is the emissivity of the body (0.80),
σ is the Stefan-Boltzmann constant (5.67 x 10^-8 W/(m^2K^4)),
T is the temperature of the body in kelvin (34 + 273.15 = 307.15 K),
T_room is the temperature of the room in kelvin (25 + 273.15 = 298.15 K),
A is the skin area of the individual (2.0 m^2).
Let's plug in these values and calculate the net loss of radiant power:
Q/t = 0.80 * (5.67 x 10^-8 W/(m^2K^4)) * (307.15^4 - 298.15^4) * 2.0
Calculating this expression will yield the result for the net loss of radiant power from the body.
b) Once you have the net loss of radiant power (in watts), you can convert it into energy in joules. Then, to find the number of food Calories (1 food Calorie = 4186 J) lost in one hour, you can divide the total energy in joules by 4186.
Let's use these steps to solve part (a) and part (b) of the problem correctly.