This applet simulates the electric field and potential for various charge distributions, including point, line, dipole, spherical and other charges. There is also a simulation, with adjustable speed, of a charge moving close to the speed of light. The field can be displayed as a velocity or force field with particles following field lines, or as field or equipotential lines. The potential and fields can be displayed in 3-D or on a movable 2-D slice. The field strength and number of particles is adjustable, and the charge can be reversed. Source code and directions (also in German) are included.