Figure shows a \(\operatorname{rod} A B\), which is bent in a \(120^{\circ}\) circular arc of ra....

Figure shows a \(\operatorname{rod} A B\), which is bent in a \(120^{\circ}\) circular arc of radius \(R\). A charge \((-Q)\) is uniformly distributed over rod \(A B\). What is the electric field \(\vec{E}\) at the centre of curvature \(O\) ?