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

JEE PHYSICS MCQ: CURRENT ELECTRICITY

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The resistance of hot tungsten filament is about

\mathrm{10}\,\,\mathrm{times}

the cold resistance. What will be the resistance of

\mathrm{100}\,\,\mathrm{W}

and 

\mathrm{200}\,\,\mathrm{V}

 lamp, when not in use?

View answer and explanation

Correct option: A

40\,\,\mathrm{\Omega }

Option A (

40\,\,\mathrm{\Omega }

) is correct because the cold resistance is calculated by dividing the hot resistance by 10, and the hot resistance is found using the power and voltage ratings.

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