There are 1029 free electrons per cubic metre of copper. For a current of 16 A in a copper wire of 1 (mm)2 cross- section, the average speed of’ ’drift’ of the free electrons along the wire is
Answer & explanation
Correct answer: option 1
$ I = nv_d Ae $
$ \Rightarrow v_d = \frac{I}{nAe} = \frac{16}{ 10^{29} \times 10^{-6} \times 1.6\times 10^{-19}} = 10^{-3} m/s$