Hi Supriya,

If I understand ur question rightly, by spped of current, u mean the fact that effects of current are seen instantly(e.g. the fan starts rotating as soon as we switch it on although the drift velocity of electrons is as low as a few cm or mm/s...)The reason for this is that when u press the switch, it is not that the electrons from the supply start moving and will hav to reach the fan.However as soon as the electrons at the supply start moving, so do the electrons in the fan motor(at the same instant) as the field is created there also.And current is jst the motion of electrons and not the complete travel of electrons from one part of the circuit to another.Thus current shows its effects instantly eventhough electrons move very slowly!!!