Two wires each of radius of cross section $r$ but of different materials are connected together end to end (in series). If the densities of charge carriers in the two wires are in the ratio $1 : 4$, the drift velocity of electrons in the two wires will be in the ratio:
Medium
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Let $n_{1}$ and $n_{2}$ be the densities of charge carriers in the two wires, $V_{d_{1}}$ and $V_{d_{2}}$ be the drift velocities of charge carriers in the two wires,
$A$ be the area of cross section,
$e$ is the charge on electron and
$I$ is the current flowing through both the wires
Hence, $I=n_{1} e A V_{d_{1}}=n_{1} e A V_{d_{2}}$
$\therefore n_{1} V_{d_{1}}=n_{2} V_{d_{2}}$
$\therefore \frac{V_{d 1}}{V_{d_{2}}}=\frac{n_{2}}{n_{1}}$
$\therefore \frac{V_{d 1}}{V_{d_{2}}}=\frac{4}{1}$
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