A few days ago a friend of mine proposed this question :
How does the current increase or decrease in a specific circuit ?
and I couldn't help but to post the question here.
Now when we increase the emf of the generator, the current in the circuit will increase proportionally according to Ohm's law:$$V=RI$$
So the question is, shall the current increase:
by an increase of the drift velocity of electrons moving across the circuit, or
by an increase of the linear density of electrons forming the current?