# Question about finding a component of the electric field

1. Oct 26, 2012

### aftershock

Let's say I have the electric potential as a function of x, y, and z: V(x,y,z)

Now I want to find the x component of the electric field along the x-axis: Ex(x,0,0)

I could take the derivative of the potential wrt x and then plug in zero for y and z.

However if I was to plug in zero for y and z in the potential function, and then derive, would that be valid?

2. Oct 26, 2012

### tiny-tim

hi aftershock!

your notation is odd … E = (Ex,Ey,Ez) = (∂V/∂x,∂V/∂y,∂V/∂z)

∂V/∂x means the derivative of V wrt x, keeping y and z fixed, so yes if you fix y = yo, z = zo, that would give you the correct value of Ex at (xo,yo,zo)