Charge \[q\] is uniformly distributed over a thin half ring of radius \[R\]. The electric field at the centre of the ring is [Roorkee 1999]

• A.            \[\frac{q}{2{{\pi }^{2}}{{\varepsilon }_{0}}{{R}^{2}}}\]
• B.                                      \[\frac{q}{4{{\pi }^{2}}{{\varepsilon }_{0}}{{R}^{2}}}\]
• C.            \[\frac{q}{4\pi {{\varepsilon }_{0}}{{R}^{2}}}\]          
• D.            \[\frac{q}{2\pi {{\varepsilon }_{0}}{{R}^{2}}}\]