Electric potential and electric field

[743344]

[SOLVED] Electric potential and electric field

Homework Statement

A - 10.0 nC point charge and a + 20.0nC point charge are 15 cm apart on the x-axis.
What is the magnitude of the electric field at the point on the x-axis, between the charges, where the electric potential is zero?

Homework Equations

sumE = E(of -10) + E (of 20)
E = kq/r^2
SumV = V(-10) +V(20)
V = kq/r

The Attempt at a Solution

let the distance at which V = 0 between the charge be x

SumV = V(-10) +V(20) = 0
k { (-10 *10^-9/0.15 - x) + (20 *10^-9/ x)} = 0
solve for x
x = 0.1
0.15 - x = 0.05

SumE = E(-10) +E(20)
k { (-10 *10^-9/(0.15 - x)^2) + (20 *10^-9/ (x)^2)} = SumE
substitute x = 0.1
Sum E= 18000 V

i don't think this is the right answer
i think i am doing something wrong

 

[rl.bhat]

The directions of the electric field due to two charges is the same. So the net field is the sum of the absolute values of the two fields.

 

[743344]

thank you