vd , thus is only due to applied
electric field on the electron 5 The relation j = r v should be applied to each type of charge carriers
separately In a conducting wire, the total current and charge density
arises from both positive and negative charges:
j = r+ v+ + r– v–
rrrrr = r+ + r–
Now in a neutral wire carrying electric current,
rrrrr+ = – r–
Further, v+ ~ 0 which gives
rrrrr = 0
j = r– v
Thus, the relation j = r v does not apply to the total current charge
density