HSC Science (Electronics) 11thMaharashtra State Board
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# A Pinhole is Made in a Hollow Sphere of Radius 5 Cm Whose Inner Wall is at Temperature 727 C. Find the Power Radiated per Unit Area. - HSC Science (Electronics) 11th - Physics

ConceptTemperature and Heat

#### Question

A pinhole is made in a hollow sphere of radius 5 cm whose inner wall is at temperature 727oC. Find the power radiated per unit area. [Stefan’s constant σ = 5.7 x 10-8 J/m2 s K4 , emissivity (e) = 0.2]

#### Solution

Given:-

T = 727 + 273 = 1000 K,

σ = 5.7 x 10-8 J/m2sK4, e = 0.2

Formula:-

(E)Q/(At)=sigmaeT^4

Calculation:- From formula,

E = 0.2 x 5.7 x 10-8 x (1000)4

= 11400

∴ E = 1.14 x 104 watt/m2

The power radiated per unit area is 1.14 x 104 watt/m2.

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Solution A Pinhole is Made in a Hollow Sphere of Radius 5 Cm Whose Inner Wall is at Temperature 727 C. Find the Power Radiated per Unit Area. Concept: Temperature and Heat.
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