(N/A) The electric field at a point in the space around a system of charges is defined as the force experienced by a unit positive test charge placed at that point,without disturbing the original system of charges.
Electric field is a characteristic property of the system of charges itself and is independent of the test charge used to measure it.
The field is defined at every point in space and its magnitude and direction may vary from point to point.
Since force is a vector quantity,the electric field is also a vector field.
The accelerated motion of charges produces electromagnetic waves,which propagate through space with the speed of light $c$.
Thus,electric and magnetic fields can be detected by their effects,specifically the forces they exert on charges.