Question

Three point charges +Q, +2Q and -3Q are placed at the vertices of an equilateral triangle ABC of side l. If these charges are displaced to the midpoints A1, B1 and C1 respectively, find the amount of work done in shifting the charges to the new locations.​

Answer 1

Answer:

METHOD 1

here work done external is asked ok

so W external =Delta U that is change of potential..

find initial potential and final and then subtract them

Ui= k (q1×q2/l+q2×q3/l+q3×q1/l)

Uf=k(2(q1×q2)/l+(q2×q3)2/l+(q3×q1)2/l) here l=l/2

finally I m getting 7 kq/l

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METHOD 2

work done is change of potential and change of potential is F×dr

so u can also use this formula to solve..