Electrostatics

JEE Main level, single correct, medium

44 of 311

Question 44 of 311

A copper rod of cross-sectional area A carries a uniform current I through it. At temperature T, if the volume charge density of the rod is ρ\rho, how long will the charges take to travel a distance d\mathrm{d} ?

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Answer: (C) ρdAI\frac{\rho \mathrm{dA}}{\mathrm{I}}

Charge density
ρ= charge  volume =qAd⇒q=ρAd Also, q=IT⇒T=qI=ρAdI\begin{aligned} &\rho=\frac{\text { charge }}{\text { volume }}=\frac{q}{A d} \Rightarrow q=\rho A d \\ &\text { Also, } q=I T \Rightarrow T=\frac{q}{I}=\frac{\rho A d}{I} \end{aligned}

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