Electric field at centre of quarter circular ring having charge density $\mathrm{\lambda }$ is ________ 

$\mathrm{Electric} \mathrm{field} \mathrm{due} \mathrm{to} \mathrm{general} \mathrm{cicular} \mathrm{arc} \mathrm{at} \mathrm{its} \mathrm{center} \mathrm{is} \mathrm{given} \mathrm{by}$

$E=\frac{\lambda }{2\pi {\epsilon }_0}\sin \left(\frac{\alpha }{2}\right), here \alpha is {90}^0$

$E=\frac{\lambda }{2\sqrt{2}\pi {ϵ}_{0}R}$