Finding the Zero Net Electric Field Point for Two Point Charges on the x-axis

[keeganisafish]

I really need help, and I'd greatly appreciate it.

"Two point charges of +10nC and -20nC lie on the x-axis at points x=0 and x=+10m, respectavly. Find the point where the net electric field is zero, if such a point exists."

The teacher gave us the answer 24m, and I just can't see how!

You help is REALLY APPRECIATED, I have been on this one forver it seems...

I keep getting 20m?

 

[himanshu121]

Show your solution sheet where u got 20 m

24m is correct

 

[keeganisafish]

I did

k*10nC     k(-20nC)
-------   --------
(10m)^2     (d-10m)^2

And solved for d

 

[himanshu121]

Originally posted by keeganisafish
I did

k*10nC     k(-20nC)
-------   --------
(10m)^2     (d-10m)^2

And solved for d

It should be
$$\frac{k*10nC}{r^2}-\frac{k*20nC}{(10+r)^2}=0$$

coz fields adds upto zero on the position left to origin

i should say for x=-24

 

[keeganisafish]

thanks!