KVPY SA Exam 2011 Question Paper

Question : 25 of 80

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A cylindrical copper rod has length L and resistance R. If it is melted and formed into another rod of length 2L. the resistance will be

Solution:

Applying volume conservation
A × L = A' × 2L

\A'=\A/2

\R={\ρL}/\A

\R'={\ρ×2\L}/\A'={\ρ×4\L}/\A

R' = 4R

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