Question

A uniform wire of resistance 100 ohm is melted and recast in to wire of length double that of the original.What would be the resistance of the new formed?

Answer 1

Answer:

Explanation:

     here volume is const AL= const

                  L1 A1 = L2 A2

         then L A = 2L A'  i.e, A' = A/2

        but R is proportional to L/A ratio

            then R1 A1 /L1 = R2 A2 / L2

               then , 100 A/L = R2 A/ 4L

         hence R2 = 400 ohm

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