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An electric bulb with tungsten filament having an area of `0.25 cm^(2)` is raised to a temperature of `3000 K`, when a current passes through it. Calculate the electrical energy being consumed in watt, if the emissivity of the filament is 0.35. Stefan's constant, `sigma = 5.67 xx 10^(-5) erg^(-1) cm^(-2) K^(-4)`. If due to fall in main voltage the fialment temperature falls to 2500 K, what will be wattage of the bulb?

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The correct Answer is:
49.19 W, 19.38 W
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