Electric Field Around A Point Charge

The animation uses physlets which were developed at

There is a point charge of unknown magnitude located at the center of the applet. The red dot is a test charge which may be moved using the mouse. The arrow drawn from the center of the test charge shows the magnitude and direction of the electrostatic FORCE. The number after the "|E|=" is the magnitude of the electric field (in Newtons per Coulomb) at the location of the test charge.  Hold down the mouse button to see the X and Y coordinates (in centimeters) of the mouse location.

By looking at the strength of the field at a particular location, calculate the magnitude of the charge located at the center. Repeat for at least 5 different points in the field. Write a lab report showing your measurements, your calculations, and your conclusion (the magnitude of the central charge).