Limits of integration for electric potential

1. Oct 22, 2015

Calpalned

In the example in the picture, we can see that they chose the limits of integration to be from 0 to R_0. Why didn't they choose x (that is, from 0 to x)? Isn't that what we normally integrate over when we find potential energy and electric fields?
Thank you

2. Oct 22, 2015

mukundpa

Here we are adding potential at P due to different ring elements. The disk is considered as large numbers of thin rings with radii varying from 0 to R0 hence the potential due to a ring element is integrated for radius 0 to R0.

3. Oct 22, 2015

Calpalned

That makes sense... so integrating from 0 to x would be invalid?

4. Oct 22, 2015

mukundpa

Yes, actually integration is the sum and we are here adding nothing which is varying with x. The distance x of P is a constant.

5. Oct 22, 2015

Calpalned

Ok thank you. I understand now

6. Oct 22, 2015

welcome.