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NEET 2016 (Phase 2) · Electrical Power & Heating Effect

Electrical Power & Heating Effect question from NEET 2016 (Phase 2)

Q47NEET 2016 · PHASE 2Medium

Electrical Power & Heating Effect

A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is

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Answer: (c)

Bulb: $R_b = \dfrac{100^2}{500} = 20\ \Omega$ , rated current $I = \dfrac{500}{100} = 5\text{ A}$ .
Total resistance needed: $\dfrac{230}{5} = 46\ \Omega$ .
$R = 46 - 20 = 26\ \Omega$ , so the answer is (c) $26\ \Omega$ .

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