Why electic potential on the center of a disk axis = 0

[moamen811]

when i saw how to get the electic potential of a charged disk at a point on its axis i found that the E.P on center of the disk =0 as
the integration of the eq:
dv = 2k(q/a^2)((r^2)+(x^2))^(.5)dr...(a) is the radius of the disk , (r) is the radius of the element and (x) is the distance between the disk and the point we get the E.P at

i found that the integration of v changed from (0---> v) and r changed from (0--->a)
and that means that when r=zero v=zero ...why??


sorry if my english is not good my native lang. is not english ...

 

[Nick89]

I am finding it hard to read your post, but I will say one thing:

A potential (be it electric or something else) is only meaningless if you look at a potential difference. For that reason, you can take your zero potential anywhere you want. You can take it in the center of the disc, or on the moon; the final answer should be the same.
However, calculations or often much simpler if you take a logic place, such as the center of the disc, or at infinity.