(1a). Black body has emissivity value of 1, but in reality, the emissivity of real objects is less than 1. Why?? (1b). The tungsten sphere of 290 mm radius is at a temperature of 31°C. If the power radiated by sphere is 93 W, calculate its emissivity value? (1c).If the same sphere is enclosed in room whose walls are kept at -7°C, what is the net flow rate of energy out of the sphere in Watts (W)

(1a). Black body has emissivity value of 1, but in reality, the emissivity of real objects is less than 1. Why?? (1b). The tungsten sphere of 290 mm radius is at a temperature of 31°C. If the power radiated by sphere is 93 W, calculate its emissivity value? (1c).If the same sphere is enclosed in room whose walls are kept at -7°C, what is the net flow rate of energy out of the sphere in Watts (W)

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter14: Heat And Heat Transfer Methods

Section: Chapter Questions

Problem 62PE: The Sun radiates like a perfect black body with an emissivity of exactly 1. (a) Calculate the...

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The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?
The Sun radiates like a perfect black body with an emissivity of exactly 1. (a) Calculate the surface temperature of the Sun, given that it is a sphere with a 7.00108m radius that radiates 3.801026W into 3-K space. (b) How much power does the Sun radiate per square meter of its surface? (c) How much power in watts per square meter is that value at the distance of Earth, 1.501011m away? (This number is called the solar constant.)
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