
Four electric charges \(+q, +q, -q\) and \(-q\) are placed at the corners of a square of side \(2L\) (see figure). The electric potential at point \(A\), midway between the two charges \(+q\) and \(+q\), is

Charges \(+q\) and \(-q\) are placed at points \(A\) and \(B\) respectively which are a distance \(2L\) apart, \(C\) is the midpoint between \(A\) and \(B\). The work done in moving a charge \(+Q\) along the semicircle \(CRD\) is
