Q.
A straight conductor of uniform cross-section carries a current i. If s is the specific charge of an electron, the momentum of all the free electrons per unit length of the conductor, due to their drift velocity only is
i=nAevd
Or vd=nAei
Total number of free electrons in the unit length of conductor, N=nA×1
Total linear momentum of all the free electrons per unit length =(Nm)vd=nAm×nAei=(e/m)i=si