The figure shows a thin rod with a uniform charge density of

The figure shows a thin rod with a uniform charge density of 2.00 microC/m. Evaluate the electric potential at point P if d = D = L/4.00.

[franciscoreneruizgonzalez]

Dude, you're the best, thanks to u, I've finally been able to understand this problem

[southmoreconlin]

If you are assuming r=sqr(x^2+d^2), you are assuming that the rod is the length from the orgin to the end. You need to take into change your limit of integration from 0 to L-D. If not, you are assuming that the section D contains charge when in reality, it does not.

[rainbowgod]

Isin't the formula for calculating the electric field q/R^2 instead of q/r

[harrymoore]

if the point you want the potential at is along the axis of the rod say a distance d from the rods length L, would you just replace r for x?