A wire of resistance 4 is stretched to twice its original length. The resistance of stretched wire would be

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Correct answer: B. (b) Resistance of a wire, R= lA=4 ⋯ (i) When wire is stretched twice, its new length be l^ '. Then l^ '=2l On stretching volume of the wire remains constant. ∴ lA=l^ 'A^ ' where A^ ' is the new cross‐sectional area or A^ '= ll 'A= l2lA= A2 ∴Resistance of the stretched wire is R^ '= l^ 'A ,= 2l(A/2)=4 lA =4 (4 )=16 (Using (i))

$A wire of resistance 4 Ω is stretched to twice its original length. The resistance of stretched wire would be$

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