Ten charges are placed on the circumference of a circle of radius R with constant angular separation between successive charges. Alternate charges 1, 3, 5, 7, 9 have charge (+q) each, while 2, 4, 6, 8, 10 have charge (–q) each. The potential V and the electric field E at the centre of the circle are respectively :

(Take V = 0 at infinity)

(1) V = 0 ; E = 0

(2) V = 10q/4π∈₀R ; E = 0

(3) V = 10q/4π∈₀R ; E = 10q/4π∈₀R²

(4) V = 0, E = 10q/4π∈₀R²