When voltage increases why does current.

Question

In a dc circuit, where a power supply connected into a circuit containing an amp meter, when you crank up the voltage of the power supply the reading of the amp meter also increases. With the definition of current being, the amount of charge passing a point per unit time. Does increasing the voltage increase the velocity of the charges, or increases the density of the charges, both or something completely different.

Answer 1

Increasing the voltage increases the velocity of the charges.  The applied voltage establishes a difference of electric potential between the connection points.  Charges arriving at one point are accelerated more on their way to the other point; hence they attain a higher velocity.  The density of the charges is a property of the conducting medium, independent of the applied voltage.