This applet allows you to see in a graphical way concepts like electric and potential fields. Furthermore, there is no danger to receive a deadly discharge.

Source code

Notes...
Instructions

The left buttons let you move, erase or place an static charge. The scrollbar define the amount of charge of the charge added. The maximum number of simultaneous charges is 10.
The buttons...

Movil

This button drops a charge in a random place with a random velocity.

Force

This simulate fiber exposed to an electric field. This image can't be animated.

Intensity

When pressed, this button takes the norm of the electric field in all points and give it a color between blue(lo[Bwer) and red(higer). If the intensity is greater than a value, the max. red is given. The same happens to the min. values.

Potential

Shows the equi-potentials. Best viewed with little charges.

Animate

If this button is pushed with a background from "Potential", "Intensity" or "Psychadelyc", the pallete of colors starts to cycle. If it is pushed again the animation is suspended. To resume, press again Animate.

Clear

This button can do several things. If there is an animation running, it's stopped. If there is a background, it is cleared. If there are only charges, all of them disapear.

Psychadelic

If there is a background (not Forces), it makes a pallete of colors with the values of the textfields (0..255). In other case, it calculates the sum of the logharitms of the distances, and give them a color. This is just to see a pretty thing. Here's one of my favorites: R1=255; R2=255; R3=255; G1=0; G2=120 ; G3=170; B1=0; B2=0; B3=0. Press a few times "Movil", then "Intensity", "Psychadelic" and finally "Animate". I call it "Un agitado día de verano". ;)