4G lI.Aalag question(1a). Black body has emissivity value of 1,but in reality, the emissivity of real objects isless than 1. Why??(1b). The tungsten sphere of 260 mm radiusis at a temperature of 33°C. If the powerradiated by sphere is 89 W, calculate itsemissivity value?(1c).lf the same sphere is enclosed in roomwhose walls are kept at -19°C, what is thenet flow rate of energy out of the sphere inWatts (W)Your storyClose Friends

a) We first define the emissivity terms, which help you to understand easily as Emissivity:- We…

Answered: (1a). Black body has emissivity val but…

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(1a). Black body has emissivity val but in reality, the emissivity of real less than 1. Why??

College Physics

10th Edition

ISBN:9781285737027

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter10: Thermal Physics

Section: Chapter Questions

Problem 24P: The Trans-Alaskan pipeline is 1 300 km long, reaching from Prudhoe Bay to the port of Valdez, and is...

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Unreasonable results. (a) Find the temperature of 0.360 kg of water, modeled as an ideal gas, at a pressure of 1.01105 Pa if it has a volume of 0.615 m3. (b) What is unreasonable about this answer? How could you get a better answer?
What mass of water at 25.0C must be allowed to conic to thermal equilibrium with a 1.85-kg cube of aluminum initially at 1.50 102C to lower the temperature of the aluminum to 65.0C? Assume any water turned to steam subsequently recondenses.
At midday when a large construction site covered with black tarps is directly under the Sun, it receives 975 W of solar power per square meter of surface from the Sun. If this hot surface loses energy only by radiation back into the atmosphere, what is its equilibrium temperature (in K)? You may use an emissivity of e = 1 for a black surface.
A sphere of radius 4.3 mm is at 3499 K. Calculate the rate of radiation of energy (in W) by the sphere, if its emissivity is 1.
he rate at which radiant energy from the sun reaches the earth's upper atmosphere is about 1.50kW/m2. the distance from the earth to the sun is 1.50*1011 m, and the radius of the sun is 6.96x108 m. if the sun radiates as an ideal black body (e=1), what is the temperature of its surface?
An astronaut performing an extra-vehicular activity (space walk) shaded from the Sun is wearing a spacesuit that can be approximated as perfectly white ( e=0 ) except for a 5 cm × 8 cm patch in the form of the astronaut's national flag. The patch has emissivity 0.300. The spacesuit under the patch is 0.500 cm thick, with a thermal conductivity k 0.0600 W/m , and its inner surface is at a temperature of 20.0 . What is the temperature of the patch, and what is the rate of heat loss through it? Assume the patch is so thin that its outer surface is at the same temperature as the outer surface of the spacesuit under it. Also assume the temperature of outer space is 0 K. You will get an equation that is very hand to solve in closed form, so can solve it numerically with a graphing calculator, with software, or even by trial and error with a calculator.
An aluminum rod 0.500 m in length and with a cross sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 3(H) K. (a) If one-halt of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool, (b) If the circular surface of the upper end of the rod is maintained at 300 K. what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 YV/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)
As the very first rudiment of climatology, estimate the temperature of Earth. Assume it is a perfect sphere and its temperature is uniform. Ignore the greenhouse effect. Thermal radiation from the Sun has an intensity (the "solar constant" S) of about 1370 W/m2 at the radius of Earth's orbit. (a) Assuming the Sun's rays are parallel, what area must S be multiplied by to get the total radiation intercepted by Earth? It will be easiest to answer in tens of Earth's radius, R. (b) Assume that Earth reflects about 30% of the solar energy it intercepts. In other words, Earth has an albedo with a value of A=0.3 . In terms of S, and R, what is the rate at which Earth absorbs energy from the Sun? (c) Find the temperature at which Earth radiates energy at the same rate. Assume that at the infrared wavelengths where it radiates, the emissivity e is 1. Does your result show that the greenhouse effect is important? (d) How does your answer depend on the area of Earth?
The thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m K and 0.020 W/m K, respectively, while other tissues inside the body have conductivities of about 0.50 W/m K. Assume that between the core region of the body and the skin sin face lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. (b) Find the rate of energy loss when the core temperature is 37C and the exterior temperature is 0C. Assume that both a protective layer of clothing and an insulating layer of unmoving air a absent, and a body area of 2.0 m2.
Some incandescent light bulbs are filled with argon gas. What is vrms for argon atoms near the filament, assuming their temperature is 2500 K?
(a) Estimate the specific heat capacity of sodium from the Law of Dulong and Petit. The molar mass of sodium is 23.0 g/mol. (b) What is the percent error of your estimate from the known value, 1230 J/kg ? `
At midday when a shopping center with a flat black roof is directly under the Sun, it receives 1,025 W of solar power per square meter of surface from the Sun. If this hot surface loses energy only by radiation back into the atmosphere, what is its equilibrium temperature (in K)? u may use an emissivity of e=1 for a black surface