# Is the electric field zero

1. Jul 8, 2006

### overkill

I have a question on how do you determine in which region will the electric field be zero.

A charge of -3.0 micro-Coulombs is located at the origin; a charge of 4.0 micro-Coulombs is located at x = 0.2m, y = 0; A third charge -97 micro-Coulombs is located at x = 0.32m, y = 0. The force on the 4.0 micro-Coulombs charge is 240N. With these configuration of three charges, where, along the x direction, is the electric field zero?

2. Jul 8, 2006

### Hootenanny

Staff Emeritus
Hi there overkill and welcome to PF,

HINT: The sum of the electric potentials from each respective charge will be zero at this point. Set 'r' as the distance from the origin.

Last edited: Jul 8, 2006
3. Jul 9, 2006

### overkill

Hi and thank you.

um...my question is how do you know in which region will the electric field be zero? to the left of all 3 charges, or between charge 1 and charge 2, or between charge 2 and charge 3, or to the right of all charges? For this problem, it is in between charge 1 and charge 2 where the electric field will be zero, but i don't understand why. Can someone explain why? Thank you.

4. Jul 9, 2006

### Staff: Mentor

Why don't you study each region in turn, writing an expression for the total field. Only in one region will it be possible for the expression to go to zero.

5. Jul 9, 2006

### arunbg

I think Hoot misread the question

6. Jul 9, 2006

### Hootenanny

Staff Emeritus
Indeed I did:zzz: