Drift Velocity of Free Electrons – Rankers Physics
Topic: Current Electricity
Subtopic: Basics of Current

Drift Velocity of Free Electrons

A copper wire of radius 1 mm contains \(10^{22}\) free electrons per cubic metre. The drift velocity for free electrons when 10 A current flows through the wire will be (Given, charge on electron = \(1.6 \times 10^{-19}\text{ C}\))
\(\frac{6.25}{\pi}\text{ m s}^{-1}\)
\(\frac{6.25 \times 10^5}{\pi}\text{ m s}^{-1}\)
\(\frac{6.25 \times 10^4}{\pi}\text{ m s}^{-1}\)
\(\frac{6.25}{\pi} \times 10^3\text{ m s}^{-1}\)

Solution:

Using the relation \(I = n e A v_d ⇒ v_d = \frac{I}{n e \pi r^2}\). Substituting the given values: \(v_d = \frac{10}{10^{22} \times 1.6 \times 10^{-19} \times \pi \times (10^{-3})^2} = \frac{6.25}{\pi} \times 10^3\text{ m s}^{-1}\).

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