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JEE Main 2005 (AIEEE) · Electrical Power & Heating Effect

Electrical Power & Heating Effect question from JEE Main 2005 (AIEEE)

Q74JEE Main 2005 · AIEEEMedium

Electrical Power & Heating Effect

The resistance of hot tungsten filament is about $10$ times the cold resistance. What will be resistance of $100\text{ W}$ and $200\text{ V}$ lamp when not in use?

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Answer: (b)

Hot resistance $R_{hot} = \frac{V^2}{P} = \frac{200^2}{100} = 400\ \Omega$ .
Cold resistance $= \frac{400}{10} = 40\ \Omega$ .
So the answer is (b) $40\ \Omega$ .

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