# Calculating the magnitude of point charges

1. Sep 12, 2010

### ezperkins

1. The problem statement, all variables and given/known data
A point charge of -6 µC is located at x = 1 m, y = -2 m. A second point charge of 12 µC is located at x = 1 m, y = 3 m.

(a) Find the magnitude and direction of the electric field at x = -1 m, y = 0.

(b) Calculate the magnitude and direction of the force on an electron at x = -1 m, y = 0.

2. Relevant equations

3. The attempt at a solution

$$\Sigma_{F}= k\frac{-6 \mu C}{8} + k\frac{12 \mu C}{13} = 1.08e4 \frac{N}{C}$$

That's for the magnitude part of A. I've already submitted to many incorrect responses, but I would like to know how to do it. Thanks ahead of time.

2. Sep 12, 2010

### hage567

You need to find both the x and y components from each charge at the point of interest and add them up accordingly to find the resultant field.

3. Sep 12, 2010

### ezperkins

I did that for another problem that asked for the respective components, why is it necessary that I so that for this problem?

4. Sep 12, 2010

### hage567

Since I don't know what the other question was, I can't tell you what's different. You need to do vector components because the point of interest is not on the same line as the two charges. It is a two dimensional situation. Have you tried what I suggested?