# Electric Field and Magnitude Problem

1. Sep 3, 2014

### pstir2

1. The problem statement, all variables and given/known data
Two identical point charges, q1 = +2.5 x 10-6 C and q2 = +2.5 x 10-6 C, are placed as shown in the diagram below. Point P is a distance 0.05 m from q1 and 0.12 m from q2, such that the angle at P is 90 degrees. Calculate the magnitude of the Electric field E at point P.

2. Relevant equations
Not sure which of these rules would apply. Also I suck at vectors
F = k x q1 x q2 / r^2

E = k x Q / r^2

3. The attempt at a solution

So I have created the diagram and I believe I have to use the second formula twice, along with some trigonometry, but I'm not sure.

E1 = k x Q1 / r^2
E1 = k x +2.5 x 10^-6 / 0.05^2
E1 = 9 x 10^6

E2 = k x Q2 / r^2
E2 = k x +2.5 x 10^-6 / 0.12^2
E2 = 1.563 x 10^6

Last edited: Sep 3, 2014
2. Sep 3, 2014

### td21

Step 1:
Decompose the E field you got at point P due to q1 to horizontal and vertical components.
Do the same for E field you got at point P due to q2.

3. Sep 3, 2014

### Staff: Mentor

That's exactly correct.

Keep going! Find the field from each charge, then find the resultant field by adding the vectors.