Equipotential surfaces are shown in figure. Then the electric field strength will be

Using dV=-E→·dr→ ⇒ΔV=-E.Δrcosθ ⇒E=-ΔVΔrcosθ ⇒E=-(20-10)10×10-2cos120° =-1010×10-2-sin30°=-102-1/2=200 V/mDirection of E be perpendicular to the equipotential surface i.e., at 120° with x-axis.