Well,
We have 2 disks of radius R where the distance between these 2 disks : $d << R$.
These disks are uniformly charged.
I have calculated the electric field near one disk, I have:
$$E(z) = \frac{\sigma}{2 \epsilon_0}\left(1 - \frac{1}{\sqrt{1 + \frac{R^2}{z^2}}}\right)$$
Now I'm stuck to find the potential between these 2 disks.
Because one disk has a positive charge and another one has a negative charge, the total electric field is
$$E_{tot} = 2E(z)$$
We know that
$$\Delta V = -\int_{+\infty}^{d}E_{tot} \cdot \mathrm dr$$
However, I get an infinite potential.
I suppose that I'm doing the wrong calculation.
The teacher explained that because $d << R$, we can approximate them as infinite planes. So, should I calculate the potential between 2 infinite planes?
Note: $z$ is the axis perpendicular to the surface of the disk.