online electrostatic simulation

Using this simulation, you can experience the phenomenon of charging a metallic ball by induction in the first stage and charging the ball by contact in the second stage after the charged rod touches the ball. The displayed charges are for an illustrational purpose, and they are not seen in reality. You can disable the display of charges on the rod and on the ball.
In this simulation, you can try two situations, one in which the rod is positively charged and another in which the rod is negatively charged, and you will see that the two situations result in the same observation.