Uniform Charge, Electric Field

[Digdug12]

Homework Statement

A very long uniform line of charge has charge per unit length 5.38 micro coulombs /m and lies along the x-axis. A second long uniform line of charge has charge per unit length -3.66 micro coulombs /m and is parallel to the x-axis at y = 0.400m. What is the net magnitude of the electric field at the point y = 0.200m? Give your answer in N/C in scientific notation to three significant digits.

Homework Equations

E=1/2pi(Epsilon)*[Uniform Charge length/R^2]

The Attempt at a Solution

I tried summing the two electric fields by using the above equation for each uniform charge and adding them together, however the answer is wrong. I also used 1/4pi(epsilon) but it was still wrong, what am i missing?

 

[LowlyPion]

Homework Statement

A very long uniform line of charge has charge per unit length 5.38 micro coulombs /m and lies along the x-axis. A second long uniform line of charge has charge per unit length -3.66 micro coulombs /m and is parallel to the x-axis at y = 0.400m. What is the net magnitude of the electric field at the point y = 0.200m? Give your answer in N/C in scientific notation to three significant digits.

Homework Equations

E=1/2pi(Epsilon)*[Uniform Charge length/R^2]

The Attempt at a Solution

I tried summing the two electric fields by using the above equation for each uniform charge and adding them together, however the answer is wrong. I also used 1/4pi(epsilon) but it was still wrong, what am i missing?

Keep i mind that the E-field is a vector field.

Add like a vector instead of just summing, because direction matters.

In this case since they are opposite signs, and your point is in the middle, your answer should be ...

|E| = |E1| + |E2|