Nodes of Ranvier

I am trying to understand why the myelin sheaths would make a difference in conduction

- I know that the axon is long so since L is proportional to resistance then the electrical current will dissipate in long distances
- If we add myelin sheaths the Area will increase so the resistance will decrease

(i'm using R= (rho*L)/A))

Now if we add myelin sheaths sodium and potassium channels will only be located where there is no myelin so at the nodes of ranvier but why does it have any effect...

Nodes of Ranvier