A certain wire A has resistance 81 Ω. The resistance of another wire B of same material and equal length but of diameter thrice the diameter of A will be: (a) 81 Ω (b) 9 Ω (c) 729 Ω (d) 243 Ω

Answer: (b). R = (ρ l)/(A) = 4ρ lπ d² ⇒ R ∝ 1d² RB = 813² = 9 Ω So the answer is (b).

A certain wire A has resistance 81 Ω. The resistance of another wire… | NEET 2023

Q13NEET 2023Easy

Ohm's Law, Resistivity & Temperature

A certain wire $\text{A}$ has resistance $81\ \Omega$ . The resistance of another wire $\text{B}$ of same material and equal length but of diameter thrice the diameter of A will be:

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Answer: (b)

$R = \dfrac{\rho l}{A} = \dfrac{4\rho l}{\pi d^{2}} \Rightarrow R \propto \dfrac{1}{d^{2}}$
$R_B = \dfrac{81}{3^{2}} = 9\ \Omega$
So the answer is (b).

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