If a point positive charge “q” is placed near another positive source charge Q, it experiences a repulsion force. If we change the position of q without receding charge Q, the force still exists with the same or a different force depending on the separation distance between the two charges. The source charge Q is said to produce or cause an electric field at all other points in its vicinity. Thus, the two particles are interacting by the fields they produce due to their charges. Therefore, you can put any point charge at point P, and it experiences a force F, you can take the point of view that the force is exerted by the field, rather than directly by charge Q.

The experimental test for the existence of an electric field at any point is simply to put a test charge at the point. If a force of electrical origin is exerted on the test charge, placed at a point, then an electric field exists at the point. Electric field is a region where electric forces act on charges when placed at any point in the region.