Finding the electric field vector along the bisector

AI Thread Summary
The discussion focuses on finding the electric field vector along the perpendicular bisector of two equal positive charges separated by distance D. The initial equation presented for the electric field was corrected to indicate that the vector direction should be along the vertical (j direction) rather than horizontal (i direction). Participants confirmed that the first part of the question was addressed correctly, while the second part requires using calculus to determine where the electric field is maximized as a function of distance. The importance of symmetry and the principle of superposition in solving the problem was emphasized. The conversation highlights the need for clarity in vector direction and the application of mathematical techniques to find maxima.
dk321
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Two equal positive charges are held fixed and separated by distance D. Find the electric field
vector along their perpendicular bisector. Then find the position relative to their center where
the field is a maximum.

so i started with symmetry and principle of superposition

and got to this answer
E = (1/(4πε))*q*D i^/( y^2 + (D^2)/4)^(3/2)

y stand for the distance from the field to the origin

is this equation the right answer for the first question? Also for the second question what changes when E is a maximum?
 
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hi dk321! welcome to pf! :smile:

(try using the X2 and B buttons just above the Reply box :wink:)
dk321 said:
E = (1/(4πε))*q*D i/( y2 + (D2)/4)3/2

nooo, draw a diagram … it isn't along i, i'ts along j, isn't it? :wink:
 
why is it j ? the two charges line in horizontal direction so along the perpendicular bisector would be in vertical direction right?
 
dk321 said:
why is it j ? the two charges line in horizontal direction so along the perpendicular bisector would be in vertical direction right?

yes, j :confused:
 
dk321 said:
Two equal positive charges are held fixed and separated by distance D. Find the electric field
vector along their perpendicular bisector. Then find the position relative to their center where
the field is a maximum.

so i started with symmetry and principle of superposition

and got to this answer
E = (1/(4πε))*q*D i^/( y^2 + (D^2)/4)^(3/2)

y stand for the distance from the field to the origin

is this equation the right answer for the first question? Also for the second question what changes when E is a maximum?

The first part is right.

Hint for second part: E is a function of 'd'. And you have to find the maxima of E(d). How about using some calculus!
 
dk321 said:
why is it j ? the two charges line in horizontal direction so along the perpendicular bisector would be in vertical direction right?

And the vertical direction is 'j'. Isnt it?
 
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