NEETPhysicsCurrent ElectricityMCQ+4 / −1
A copper wire of radius contains free electrons per cubic metre. The drift velocity for free electrons when current flows through the wire will be (Given, charge on electron ) :
- A
- B
- C
- D
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Correct answer: B
$$ \begin{aligned} & \mathrm{I}=\mathrm{neAV_{d }} \\ & \mathrm{V}_{\mathrm{d}}=\frac{\mathrm{I}}{\mathrm{neA}}=\frac{10}{10^{22} \times 1.6 \times 10^{-19} \times \pi \times 10^{-6}} \\ & \mathrm{~V}_{\mathrm{d}}=\frac{6.25}{\pi} \times 10^3 \mathrm{~m} / \mathrm{sec} \end{aligned} $$
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