Physics
posted by Paul .
An infinitely long line charge of uniform linear charge density λ = 3.00 µC/m lies parallel to the y axis at x = 2.00 m. A point charge of 4.70 µC is located at x = 1.50 m, y = 2.50 m. Find the electric field at x = 2.50 m, y = 2.00 m.
I get 23.7 kN/C, why is that wrong?

I haven't done the calcs, but how can you just have a magnitude? This is a vector addition of two components of E.

yes, I added the vectors, of the charges. for a uniform line, E= kλ/R. Since the charge on the line is negative, it goes towards the line, and only has an x component of E= 12 kN/C. For the point charge, which is negative, E is away from the source, I got E=30.2 kN/C for the x component, and 15.1 kN/c for the y component. I added the x components, and then found the final magnitude with sqrt(x^2+y^2) as 23.7kN/C. But that is the wrong answer.