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JEE Mains · Physics · STD 12 - Current electricity
  • JEE Mains 2025
  • Medium
  • MCQ

A wire of resistance R is bent into an equilateral triangle and an identical wire is bent into \(a\) square. The ratio of resistance between the two end points of an edge of the triangle to that of the square is:

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Answer & Solution

Correct Answer

(C) \(32 / 27\)

Step-by-step Solution

Detailed explanation

For the wire bent into an equilateral triangle, each side has a resistance \(\frac{R}{3}\).

\(R_{\text {eq }}=\frac{\left(\frac{2 R}{3}\right)\left(\frac{R}{3}\right)}{\frac{2 R}{3}+\frac{R}{3}}=\frac{2 R}{9}=R_1\) (lets say)
For the wire bent into a square, each side has a resistance \(\frac{R}{4}\).

\(\begin{aligned} & R_{\text {eq }}=\frac{\left(\frac{3 R}{4}\right)\left(\frac{R}{4}\right)}{\frac{3 R}{4}+\frac{R}{4}}=\frac{3 R}{16}=R_3 \text { (lets say) } \\ & \Rightarrow \frac{R_1}{R_3}=\frac{\frac{2 R}{9}}{\frac{3 R}{16}}=\frac{32}{27}\end{aligned}\)
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