Consider rectangle PQRS of sides 20cm and 15cm with charges 2microC, 4microC, 9microC at P, Q and S respectively. Determine the resultant electric field intensity at the fourth corner, R of the rectangle due to the charges P, Q and S.
Hence determine the resultant force that would act on a fourth charge 6microC placed at point R due to the other charges at P, Q and S.