Advertisements
Advertisements
Question
Assume that the total surface area of a human body is 1.6 m2 and that it radiates like an ideal radiator. Calculate the amount of energy radiated per second by the body if the body temperature is 37°C. Stefan constant σ is 6.0 × 10−8 W m−2 K−4.
Advertisements
Solution
Given:
Area of the body, A = 1.6 m2
Temperature of the body, T = 310 K
From Stefan-Boltzmann law,
`"Energy radiated"/"Time" = sigma"AT"^4`
Here, A is the area of the body and `sigma` is the Stefan-Boltzmann constant.
Energy radiated per second = 1.6 × 6 × 10−8 × (310)4
= 886.58 ≈ 887 J
APPEARS IN
RELATED QUESTIONS
Why does blowing over a spoonful of hot tea cools it? Does evaporation play a role? Does radiation play a role?
Cloudy nights are warmer than the nights with clean sky. Explain
Why is a white dress more comfortable than a dark dress in summer?
A solid at temperature T1 is kept in an evacuated chamber at temperature T2 > T1. The rate of increase of temperature of the body is proportional to
The left end of a copper rod (length = 20 cm, area of cross section = 0.20 cm2) is maintained at 20°C and the right end is maintained at 80°C. Neglecting any loss of heat through radiation, find (a) the temperature at a point 11 cm from the left end and (b) the heat current through the rod. Thermal conductivity of copper = 385 W m−1°C−1.
A solid aluminium sphere and a solid copper sphere of twice the radius are heated to the same temperature and are allowed to cool under identically surrounding temperatures. Assume that the emissivity of both the spheres in the same. Find the ratio of (a) the rate of heat loss from the aluminium sphere to the rate of heat loss from the copper sphere and (b) the rate of fall of temperature of the aluminium sphere to the rate of fall of temperature of the copper sphere. The specific heat capacity of aluminium = 900 J kg−1°C−1 and that of copper = 390 J kg−1°C−1. The density of copper = 3.4 times the density of aluminium.
A cylindrical rod of length 50 cm and cross sectional area 1 cm2 is fitted between a large ice chamber at 0°C and an evacuated chamber maintained at 27°C as shown in the figure. Only small portions of the rod are inside the chamber and the rest is thermally insulated from the surrounding. The cross section going into the evacuated chamber is blackened so that it completely absorbs any radiation falling on it. The temperature of the blackened end is 17°C when steady state is reached. Stefan constant σ = 6 × 10−8 W m−2 K−4. Find the thermal conductivity of the material of the rod.
Wein's constant is 2892 × 10-6 SI unit and the value of λm for moon is 14.46 micron. The surface temperature of moon is ______.
A student says, "Heat from the Sun reaches Earth because air carries it across space." Which statement best explains why this is incorrect?
You place your hands near a burning candle and feel warmth on both sides of the flame. What does this observation mainly show?
Why are cooking utensils like pans made of metal but fitted with plastic or wooden handles?
According to Stefan–Boltzmann Law, if the temperature of a body is doubled (in Kelvin), the heat emitted by it becomes ______.
A perfect black body has an emissivity value of ______.
Thermal radiation is described as a two-step process. Which of the following correctly identifies both steps in the correct order?
In the experiment where a test tube of water is heated from the top with ice at the bottom, the ice does not melt. What is the primary reason for this?
