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The operating temperature of a tungesten...

The operating temperature of a tungesten filament in an indandescent lamp is `2000 K ` and its emissivity is `0.3`.
Find the surface area of the filament of a `25` watt lamp. Stefan's constant ` sigma = 5.67xx10^(-8) Wm^(-2)K^(-4)`

Text Solution

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`because ` Rate of emission = wattage of the lamp
` therefore` `W= AesigmaT^(4) implies A=(W)/(esigmaT^(4)) = (25)/(0.3 xx 5.67 xx 10^(-8) xx (2000)^(4)) = 0.918m^(2)`
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