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Question
Two bulbs are marked 100 W, 220 V and 60 W, 110 V. Calculate the ratio of their resistances.
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Solution
Given Ist Bulb
P1 = 100 W
V1 = 220 V
IInd Bulb
P2 = 60 W
V2 = 110V
We know P = `"V"^2/"R"`
So R = `"V"^2/"P"`
So `"R"_1/"R"_2 = ("V"_1^2/"P"_1)/("V"_2^2/"P"_2)`
`= ("V"_1^2 xx "P"_2)/("P"_1 xx "V"_2^2)`
`= (220^2 xx 60)/(100 xx 110 xx 110) = 2.4`
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