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Homework Statement
 a) A point charge + q is placed at the origin. By explicitly calculating the relevant line integral, determine how much external work must be done to bring another point charge + q from infinity to the point r2= aŷ ? Consider the difference between external work and work done by the force. {2}
 b) Both of these charges are held fixed and a third charge + q is now brought from infinity to position r= ax̂ + ay.̂ Repeat the same type of calculation as in a). What is the total stored potential energy of this threecharge system? {2}
Homework Equations
U=W=∫ F.dr
The Attempt at a Solution
check the image[/B] for my full solution
My question is why do i need to include the sqrt(2) in the highlighted part, shouldn't it be sqrt(2)*a because that is the distance between those 2 points. Any explanation is much appreciated :)
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