> For a given voltage, Ohm's law tells us that if we increase the resistance, then the current must decrease.
>
>But what's actually happening to decrease the current?

*If we increase the potential*, the current increases, rest all the parameters are constant - which are resistance, material, temperature etc. Drift velocity of the charges, here, have increased due to increased potential. 

Drift velocity is $v_d = \frac{e.V.d.\tau}{m}$, where 

$e$ - charge 

$V$ -  Potential

$d$ - distance moved by the charge in time $\tau$ 

$m$ - mass of the charge

So here we can say that **Charges move with greater speed now** 



*Now to change the resistance*, let us just change resistivity i.e changing the material and rest all the parameters are same except "Free Charge Density of the material", it depends on the material. 

Current, $I = n.e.A.v_d$, here $(n.e)$ is the charge density, the effective charge that is flowing per unit volume.

So here **the amount freely flowing charge changes** and also the **drift velocity changes** because $\tau$, the effective time between consecutive collisions, may also change.