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Most Important Selected Qs for JEE AdvancedPhysicsThermal Properties of Matter

A small sphere ( . emissivity =0.9 , radius .=r₁ ) is located at the centre of a spherical asbestos shell (thickness =5.0 ~cm , outer radius = r ₂ ). The thickness of the shell is small compared to the inner and outer radii of the shell. The temperature of the small sphere is 800 K , while the temperature of the inner surface of the shell is 600 K . The temperature of small sphere is maintained constant. Assuming tha

Correct answer

0516

Step-by-step solution

dQ dt = 0.8 4 r ₁^2 [800^4-600^4 ]= k 4 r ₂ r ₂^ r ₂^ - r ₂ (600- T ) r ₂ r ₂^ r ₂^2600- T = 17 3 10⁻⁸ 0.9 10 1 100 10^8 100 28 10^3 5 100 0.085 ~T =516 ~K

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