Equipotential surfaces are shown in figure. Then the electric field strength will be
100 vm-1 along X-axis
100 vm-1 along Y-axis
200 vm-1 at an angle 120° with X-axis
50 vm-1 at an angle 120° with X-axis
Using dV=-E→·dr→ ⇒ΔV=-E.Δrcosθ ⇒E=-ΔVΔrcosθ ⇒E=-(20-10)10×10-2cos120° =-1010×10-2-sin30°=-102-1/2=200 V/m
Direction of E be perpendicular to the equipotential surface i.e., at 120° with x-axis.