Next, *V* is turned up slightly so that the oil droplet rises with a new terminal velocity *v _{2}*.

We have:

Note that the electric force is acting upwards (since the oil droplet is rising); upthrust is also acting upwards (since the pressure is still greater below the object than above it due to the exponential distribution of air); drag is now acting downwards since the oil droplet is rising and weight remains acting downwards due to the effect of gravitational force. Substituting eq2, eq3 (with *v _{2}*

*instead of*

_{ }*v*), eq4 and eq7 in eq 11, we have

_{1}Substituting eq5 in eq12:

Substituting eq8 in eq13 and rearranging:

Once again, Millikan recorded the distance travelled by the rising oil droplet over a period of time and calculated the new terminal velocity, *v _{2}*.

Substituting the values of *v _{1}*,

*v*and the calculated value of

_{2 }*r*(from eq6) in eq14, Millikan determined a value for

*q*. He repeated the experiment multiple times, each time varying the strength of X-rays ionizing the air, resulting in a varying number of electrons attaching to the oil droplet. He then obtained various values of

*q*and found them to be multiples of 1.5924 x 10

^{-19 }C. Millikan concluded that the value of 1.5924 x 10

^{-19 }C is equal to the charge of a single electron. Subsequent determinations refined that value to 1.602176487 x 10

^{−19}C.

Using the Faraday constant and the value of the charge of a single electron that he determined, Millikan calculated the Avogadro constant and proved that one Faraday is the quantity of charge for one mole of electrons.