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JEE Mains · Physics · STD 12 - Current electricity
  • JEE Mains 2022
  • Medium
  • MCQ

A \(1\,m\) long wire is broken into two unequal parts \(X\) and \(Y\) The \(X\) part of the wire is streched into another wire \(W\). Length of \(W\) is twice the length of \(X\) and the resistance of \(W\) is twice that of \(Y\). Find the ratio of length of \(X\) and \(Y\).

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Answer & Solution

Correct Answer

(B) \(1: 2\)

Step-by-step Solution

Detailed explanation

\(\frac{ R _{ X }}{ R _{ Y }}=\frac{\ell_{ X }}{\ell_{ Y }}\)

When wire is stretched to double of its length, then resistance becomes 4 times

\(R _{ W }=4 R _{ X }=2 R _{ Y }\)

\(\frac{ R _{ X }}{ R _{ Y }}=\frac{1}{2}\)

So. \(\frac{\ell_{ X }}{\ell_{ y }}=\frac{1}{2}\)

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