# Homework Help: Field strength!

1. Feb 10, 2008

### jalen

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

+1.5x10^-6C, +3.0x10^-6C, 0.20m

2. Relevant equations

Two charges of +1.5x10^-6C and +3.0x10^-6C are 0.20m apart. Where is the electric field between them equal to zero?

3. The attempt at a solution

= (9.0x10^9)(1.5x10^-6C) + (9.0x10^9)(3.0x10^-6C)
x^2 (0.2-x)^2
1.5(0.2-x)^2=3.0(x^2)
(0.2-x)^2=2(x^2)
0.4-0.2x-0.2x+x^2=2x^2
-x^2-0.4+0.04=0

The answers you'll get are -0.48 and 0.08. The answer in the text is 1.2x10^-1m and you can get it if it's 0.06 instead of 0.04. I looked over my work but I can't find where I went wrong. =(

2. Feb 10, 2008

### rock.freak667

The electric field strength due to Q1(at distance x from Q1)=The electric field strength due to Q2(at the distance of x from Q2)

3. Feb 10, 2008

### jalen

Sorry, I don't really understand what you're trying to say. Can someone please tell me which line is incorrect so I can take a closer look and figure it out again.