JEE Mains · Physics · STD 12 - 3. current electricity
A wire of resistance \(R_{1}\) is drawn out so that its length is increased by twice of its original length.The ratio of new resistance to original resistance is.
- A \(9: 1\)
- B \(1: 9\)
- C \(4: 1\)
- D \(3: 1\)
Answer & Solution
Correct Answer
(A) \(9: 1\)
Step-by-step Solution
Detailed explanation
\(R _{1}=\rho \frac{ L _{1}}{ A _{1}}\) \(R _{2}=\rho\left(\frac{3 L _{1}}{ A _{1} / 3}\right)=9 \rho \frac{ L _{1}}{ A _{1}}\) \(\therefore \frac{ R _{2}}{R _{1} }=9\)
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