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Question
Two lamps are rated 220V, 50W and the other rated 220V, 100W are connected in series with the mains of 220 V. Explain, why the 50W lamp glows more?
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Solution
From relation R = V2/P, the resistance of filament of 50W lamp will be more than that of 100W lamp. If the two lamps are connected in series with the mains, same current will flow through each lamp. From relation H = I2Rt, since resistance of 50W lamp is more than that of 100W lamp, so the 50 W lamp will consume more electrical energy than that of 100W lamp, in the same time. Hence the 50W lamp will glow more.
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