CUET · PHYSICS · PYQ PAPER 2025
A cylindrical wire is stretched to increase its length by 10%. The percentage increase in resistance will be
- A \(10 \%\)
- B \(15 \%\)
- C \(21 \%\)
- D \(32 \%\)
Answer & Solution
Correct Answer
(C) \(21 \%\)
Step-by-step Solution
Detailed explanation
\(R = \rho \frac{L}{A}\) \(V = AL \implies A = V/L\) \(R = \rho \frac{L^2}{V}\) \(L' = 1.1L\) \(R' = \rho \frac{(1.1L)^2}{V} = 1.21 \rho \frac{L^2}{V} = 1.21R\) Percentage increase \( = \frac{R' - R}{R} = \frac{1.21R - R}{R} = 0.21 \)
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