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Current Electricity question

2023 · Q140
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Current Electricity question

2023 · Q140

NEETPhysicsCurrent ElectricityMCQ+4 / −1

A certain wire A\mathrm{A}A has resistance 81 Ω81 ~\Omega81 Ω. The resistance of another wire B\mathrm{B}B of same material and equal length but of diameter thrice the diameter of A will be :

  1. A
    81 Ω81 ~\Omega81 Ω
  2. B
    9 Ω9 ~\Omega9 Ω
  3. C
    729 Ω729 ~\Omega729 Ω
  4. D
    243 Ω243 ~\Omega243 Ω
View written solutionFree

Correct answer: B

$$\mathrm{R=\frac{\rho L}{A}}$$

If diameter becomes thrice then cross section area will become 9 times so

$$\mathrm{R\propto \frac{1}{A}}$$

Resistance will become $\frac{1}{9}$ times

$$\mathrm{R'=\frac{81\Omega}{9}=9\Omega}$$

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