# Uniform line of charge and point charge

## Homework Statement

An infinite line charge of uniform linear charge density lambda = -3.1 mu or micro CC/m lies parallel to the y axis at x = -1 m. A point charge of 0.7 mu or micro CC is located at x = 2.5 m, y = 3.5 m. Find the x- and y-components of the electric field at x = 3.5 m, y = 3.0 m.

flux = E*A = Q/ε
E = kQ/r^2

## The Attempt at a Solution

X axis:
To find the electric field from the line only: gaussian cylinder, centered on the line and r = 4.5m.
E*2∏*4.5*L = λL/ε -> E1 = λ/(ε*9*∏) to the left

From the point:
E2 = K(.7*10^-6)/1.25*sin(63.43°) to the right

Ex = E2-E1 Right?

Y axis:
The line don't matter because it cancels itself out. right?
Ey = K(.7*10^-6)/1.25*cos(63.43°) Down

Both answers need to be in kN/C, I'm at a loss, do you guys have any ideas? I have tried many different answers and I've checked all of the units.

Last edited:

## Answers and Replies

TSny
Homework Helper
Gold Member
Your work looks good to me. What did you get for your final answer?

ehild
Homework Helper
What are your numerical results?

ehild

TSny
Homework Helper
Gold Member
• 1 person
Welp, I just found my mistake. Damn Radians!