Question

A wire, 1.2mm in diameter and 32 cm long, carries a current of 648 ma. The density of free electrons in the wire is 5.90 × 1028m-3.The drift velocity of electrons in the wire is:

Answer 1

Volume of wire = $\pi$ * ($d^{2}$ / 4) * l

                          = 3.14 * ((0.0012*0.0012)/4) * 0.032

                          = 3.6 * $10^{-8}$

Current = number of electrons * e * Drift velocity

Drift velocity = Current / (number of electrons * e)

                     = 0.648 / (3.6 * $10^{-8}$ * 5.90 * $10^{28}$ * 1.6 * 10 * $10^{-19}$ )

                     = 0.00019067796 m/sec