Electric Field of a Point Charge
This Demonstration shows the magnitude and direction of the electric field from a point charge. Drag the locator or vary the source charge to show that the electric field is proportional to the source charge. Keep the source charge constant and drag the locator to see how the electric field depends on distance. You will find an inverse square law of force. Place a small test charge at some location in the electric field to determine the electrostatic force it experiences.