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(C) The drift velocity $v_{d}$ is given by the formula $v_{d} = \frac{I}{neA}$,where $I$ is the current,$n$ is the electron density,$e$ is the charge

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$v_{d}/2$

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(C) The drift velocity $v_{d}$ is given by the formula $v_{d} = \frac{I}{neA}$,where $I$ is the current,$n$ is the electron density,$e$ is the charge of an electron,and $A$ is the cross-sectional area.Since $I = \frac{E}{R}$ and $R = \rho \frac{l}{A}$,we have $I = \frac{E A}{\rho l}$.Substituting this into the drift velocity formula:$v_{d} = \frac{E A}{\rho l n e A} = \frac{E}{\rho l n e}$.From this expression,we see that $v_{d} \propto \frac{1}{l}$.If the length is changed to $l' = 2l$,the new drift velocity $v_{d}'$ is:$v_{d}' = \frac{E}{\rho (2l) n e} = \frac{1}{2} \left( \frac{E}{\rho l n e} \right) = \frac{v_{d}}{2}$.

An electric cell of emf $E$ is connected across a copper wire of diameter $d$ and length $l$. The drift velocity of electrons in the wire is $v_{d}$. If the length of the wire is changed to $2l$,the new drift velocity of electrons in the copper wire will be

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