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Alv95
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Homework Statement
I have to find a general equation to find the magnitude of the resultant electrical field vector on a positive test charge by two charges of the same magnitude but opposite signs.
The two charges are equidistant from the y-axis and are on the x-axis.
Q1= positive charge
Q2= negative charge
a= distance between a charge and the y-axis
(x;y)= coordinates of the test charge
k ( constant) = 899 000 000
Homework Equations
All electromagnetism related equations
The Attempt at a Solution
I found the distance r1 between Q1 and the test charge:
[tex]\sqrt{(x+a)^2+y^2}[/tex]
I found the distance r2 between Q2 and the test charge:
[tex]\sqrt{(x-a)^2+y^2}[/tex]
I found the magnitude of E1:
[tex]\frac{kQ}{r1^2}= \frac{kQ}{(x+a)^2+y^2}[/tex]
I found the magnitude of E2:
[tex]\frac{kQ}{r2^2}= \frac{kQ}{(x-a)^2+y^2}[/tex]
I found the angle β between E1 and the x-axis:
[tex]\arctan{(\frac{y}{x+a})}[/tex]
I found the angle γ between E2 and the x-axis:
[tex]\arctan{(\frac{y}{x-a})}[/tex]
I found the x component of E1:
[tex]E1\cos{β}= \frac{kQ}{(x+a)^2+y^2}\cos(\arctan{(\frac{y}{x+a})})[/tex]
I found the x component of E2:
[tex]E1\cos{γ}= \frac{kQ}{(x-a)^2+y^2}\cos(\arctan{(\frac{y}{x-a})})[/tex]
I found the y component of E1:
[tex]E1\sin{β}= \frac{kQ}{(x+a)^2+y^2}\sin(\arctan{(\frac{y}{x+a})})[/tex]
I found the y component of E2:
[tex]E1\sin{γ}= \frac{kQ}{(x-a)^2+y^2}\sin(\arctan{(\frac{y}{x-a})})[/tex]
At this stage I thought of doing the sum of te x and y components and then use the pythagorean theorem but I'm not sure of the signs... Is it right? Do you have any Idea on how to do it?
I have to find an always valid equation :)
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