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Physics - Current Electricity Question with Solution | TestHub

PhysicsCurrent ElectricityEquivalent ResistanceEasy2 minPYQ_2019

PhysicsEasysingle choice

The electric resistance of a certain wire of iron is $R$ . If its length and radius are both doubled, then

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Solution:

$R_{1} = \frac{ρ ℓ _{1}}{A _{1}}$ , now $ℓ_{2} = 2 ℓ_{1}$ and $r_{2} = 2 r_{1}$ $A_{1} = π r_{1}^{2} A_{2} = π (r_{2})^{2} = π (2 r_{1})^{2} = 4 π r_{1}^{2} = 4 A_{1} R_{2} = \frac{ρ ℓ _{2}}{A _{2}} ∴ R_{2} = \frac{ρ ( 2 ℓ _{1} )}{4 A _{1}} = \frac{ρ ℓ _{1}}{2 A _{1}} = \frac{R _{1}}{2}$ $∴$ Resistance is halved, but specific resistance remains the same.

Stream:VITEEESubject:PhysicsTopic:Current ElectricitySubtopic:Equivalent Resistance

⏱ 2mℹ️ Source: PYQ_2019

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