- #1

ArtemRose

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## Homework Statement

I was given this assignment for homework, and got it wrong, but now I'm studying for the first exam, and I still can't find out where I went awry. The problem is:

A charge per unit length λ = +8.00 μC/m is uniformly distributed along the positive y-axis from y = 0 to y = +a = +0.500 m. A charge per unit length λ = -8.00 μC/m, is uniformly distributed along the negative y-axis from y = 0 to y = –a = -0.500 m. What is the magnitude of the electric field at a point on the x-axis a distance x = 0.371 m from the origin?

1.567×105 N/C

**This being the answer I am supposed to get.**

## Homework Equations

Now, I know that I can find this using the calculus with dE=k*(dq/r^2) dy

## The Attempt at a Solution

Now, set the equation to be dE=k*lambda*y/(y^2 + (.371)^2)^(3/2) dy

Then when I took the derivative, it would be then E=k*lambda/(sqrt(y^2 + (.371)^2) + Constant

And then I plug in for y, but it's nowhere near the right answer. Where am I going wrong? I've tried another method to solve for line of charge

[ ((k*8e-6)/.371)*(.5/sqrt(.5^2 + .371^2)) ] (that is, [ ((k*lambda)/x)*(y/sqrt(y^2 + x^2)) ] equaling the E Field.

without using calculus, and that gave me an answer within the bounds, but I didn't have to double it when it should be giving me only the answer for one of the lines of charge, so that makes me doubt that method.

Any ideas?