The force depends on the distance to the fixed charge.
In case of two same sign particules, the test particule is accelerated outward.
In case of two opposite sign particules, the typical trajectory of the test particle is an ellipse similar to gravitational orbits.
The force is always tangent to the field lines.
Click on the static charge in the center to change its sign.
Click on the moving charge to catch it, then “ throw it” to set new initial conditions.