2024 Re-NEET Current ElectricityResistance, resistivity and combination of resistors Medium Question 15 of 130 in Current Electricity

A uniform metal wire of length l has 10 $\Omega$ resistance. Now this wire is stretched to a length 2l and then bent to form a perfect circle. The equivalent resistance across any arbitrary diameter of that circle is

A 10 $\Omega$
B 5 $\Omega$
C 40 $\Omega$
D 20 $\Omega$

The answer is A.

Solution

Since $R\propto l^2$ (volume constant), stretching to length $2l$ gives $R_0=4\times10=40\ \Omega$. Bending into a circle, the diameter divides it into two equal arcs of $20\ \Omega$ each in parallel: $R_{AB}=\dfrac{20\times20}{20+20}=10\ \Omega$.

Concept Resistance, resistivity and combination of resistors

Current Electricity in past papers

130 questions from this chapter have appeared across 27 exam years.