# Someone verify?

1. Jan 29, 2005

### Winner

I have two charges, one is -16uC and the other +4uC. They are separated by 3.0m. I have to find the point in which the electric field is = 0 .

Is my diagram here correct? (I mean are the lengths of the arrows correct with respect to magnitude of attraction between the two)

-16uC -->E=0<----------- +4uC.
<------------------->
3.0m

2. Jan 29, 2005

### Parth Dave

if the electric field at point r is zero than a point charge placed at point r will experience no force. Now, if we look at your problem. Suppose we place a negative charge somewhere in between the two particles. How will it interract with the other two? (Pay close attention to the direction of the force and electric field)

3. Jan 29, 2005

### Winner

ok...
Maybe like this:

-16uC ---- (-C) ---> --- <----- +4uC.

Repel away from -16 and go towards +4.

4. Jan 29, 2005

### Winner

So is something wrong with my first diagram?
-16uC -->E=0<----------- +4uC. ?

or maybe it should be

-16uC ------------->E=0<-- +4uC. I think the first one looks more correct.

5. Jan 29, 2005

### Parth Dave

Yes, exactly. If the charge is placed in between the two particles, it will be repelled by one and attracted by the other. Therefore, both of the two particles will force it in the same direction. If that is true, how is it possible for the forces to cancel out?

I don't believe either of the two are correct.

6. Jan 29, 2005

### Winner

Last effort lol. Is this right?

-16uC <-------------E=0--> +4uC.

7. Jan 29, 2005

### Winner

Wait a min, it doesn't have to between the two...

So wait, it could be

<---------------------
-16uC ___________________+4uC---->d where (E=0)
?

8. Jan 29, 2005

### Parth Dave

Now thats better, youre right, it doesn't have to be between the two. Now which side would it have to be on?

9. Jan 29, 2005

### Winner

The right side lol! I should make the electric fields equal as in E=k(q)/d^2.