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The operating temperature of an in cande...

The operating temperature of an in candescent bulb (with tungsten filament) of power 60 W is 3000 K. If the surface area of the filament be 25 `mm^2`, find its emissivity e.

Text Solution

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Given `T=3000K`, power`=(dQ)/(dt)=60W`
Area `A=25xx10^-6m^2`,`e=?`
Using Eq. (i) , we have, total radiation lost per second
`=(dQ)/(dt)=AesigmeT^4`
`60W=(25xx10^-6m^2)e(5.67xx(10^-8)/(m^2-K^4))(3000)^4K`
`60=114.82e`
`e=0.52`
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