Q.

The potential of electrostatic field is given by ϕ=xy, where x & y are coordinate. Which of the following is correct

1 Electric field at all points on positive x-axis is in positive y-direction.  
2 Electric field at all points of positive y-axis is in negative x-direction.  
3 Electric field at (2, 2) is 2N/m.  
4 Electric field at x,y makes an angle θ=tan-1(yx) with x-axis  

Ans.

(2)

E=-yi^-xj^,    tanθ=EyEx=xy