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Uniform line of charge and point charge

  • Thread starter noagname
  • Start date
1. The problem statement, all variables and given/known data
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.

2. Relevant equations
flux = E*A = Q/ε
E = kQ/r^2

3. 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:


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


Homework Helper
What are your numerical results?

Welp, I just found my mistake. Damn Radians!

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