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Hi.
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Here in this given problem this is an equilateral triangle.
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Let it be represented as a, b, c.
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Three charges at the three vertices q each and the side of equilateral triangle that is given as a.
00:31
Then the center of this equilateral triangle, center which is the point.
00:37
Of intersection of the three medians of the equilateral triangle and we know these distances are each a -o is equal to b -o is equal to c -o and if we assume it to be r it is actually two -third of the length of the median of the equilateral triangle medium means this perpendicular bisector of any of the side of this triangle let this point to be d so this median means ad that will be given by because this angle will be 30 degree half of the vertex angle a vertex angle which is 60 degree so that is a b cost 60 degree sorry a b cost 30 degree means we can say this is a root 3 by 2.
01:50
So the distance of observation point o from each vertex that is 2 third of the length of the median means a root 3 by 2 canceling this 2 finally this is a root 3 by 3.
02:09
Now at the center of this triangle there are 3 electric fields as electric field goes away from the positive charge so this is e because of a then e because of b going like this away from b and e because of c going like this and all these three electric fields will be equal in magnitude ea is equal to e b is equal to e c and using the expression for electric field that is kq by r square means this is k q by for r that is a root 3 by 3 square so here it becomes 3 k q by a square now we can resolve e c and e b into components your horizontal components will cancel each other and vertical components in upward direction will be added and these components are ec, e b because this angle will be 60 degree for both so this is e b cost 60 degree plus e c cos 60 degree in upward direction and this so there are two elective fields now at this center one is e in downward direction e down which is equal to ea means 3k q by a square.
03:54
And in upward direction e up, that is e b, cost 60 degree plus ec cost 60 degree...