# Electric Potential vs Electric Field?

I've read that in an electric field due to it being a vector if its mirrored symmetrically the components cancel out. However, the electric potential is a scalar so the components are added not canceled out. This is consistent with one question in my physics H.W., but not for another question. So i'm very confused as to when electric potential cancels out and when it sums up.

The question where it is consistent that the electric potential adds up is # 25.47 here:
http://web.unbc.ca/~hussein/Phys_111_Winter_2005/Selected_Ch25.pdf

However for the following question the y components cancels out according to the answer.

Q.) A uniformly charged insulating rod of length 14.0 cm is bent into the shape of a semicircle as shown in Figure P25.44. The rod has a total charge of 27.50 mC. Find the electric potential at O, the center of the semicircle.

This is figure 25.44 http://www.webassign.net/serpop/p19-21.gif

Khashishi
There is no "y component" of the potential since it's a scalar. You just add together or integrate the potential from each source point.

There is no "y component" of the potential since it's a scalar. You just add together or integrate the potential from each source point.

So you always completely disregard 'y' ? Seems wrong.

DrClaude
Mentor
So you always completely disregard 'y' ? Seems wrong.
No, there is no "y component" to disregard, because there is no "y component" to start with. The potential is a scalar, not a vector with x and y components.

Anyway, this a homework-type problem, so it will have to be posted in the homework forum, with an attempt at a solution.