Irodov Problem 3.45

In Problem 3.44 Eqn (1) we have already determined the electric field due a disc as,


The Electric field due to a negative and positively charged discs is then given by,



When l is very small, using Taylor's series on l for (2) we have,



When we can further approximate (3) as,



We can now find the electric potential at a distance x approaching from the positive direction as,



Similarly the electric potential at a distance x approaching from the negative direction is given by,