# Electric field midway between an electron and proton. Help!

1. Dec 12, 2013

### astru025

1. The problem statement, all variables and given/known data

What is the electric field midway between an electron and a proton separated by 0.8 nm?

2. Relevant equations
E=kQ / r^2 . 9E9 x 1.6 E-19 / .(.8E-9)^2

3. The attempt at a solution
Any help would be nice!

2. Dec 12, 2013

### hjelmgart

Calculate the electric field at that point between them with the formula you wrote for both the proton and the electron. Then add these and you get the total electric field at that point.

3. Dec 13, 2013

### astru025

Thank you. So I take 9E9 x 1.6E-19 / (.8E-9)^2 = 2.25E9 and then times this by 2??? Please let me know if this looks right! Thanks

4. Dec 13, 2013

### hjelmgart

Yeah, that should do, because the electric fields add up, when between a negative and a positive charge. You can show this by drawing the field lines from each charge.

5. Dec 14, 2013

### astru025

So I get 4.5E9 which still proves to be incorrect. My answer needs to be in N/C but this answer is in N/C correct?

6. Dec 15, 2013

### hjelmgart

Oh right, you are putting r=0.8, but you need to find the electric field midway between them (r=0.4).
Regarding the units, you should figure that out on your own by putting the correct units for each term in the equation, but yes you will get the correct units.