Final answer:
Charges move on a conductor connected to ground due to electrical forces seeking electrostatic equilibrium. Free electrons or ions in the conductor move until the excess charge flows into the ground, neutralizing the conductor.
Step-by-step explanation:
When a (small) charged conductor is connected to ground, any excess charges on the conductor will move because of the electrical forces within the conductor.
Conductors contain free charges that can easily move; these are primarily the free electrons in metals or the free ions in electrolyte solutions.
The movement of these charges will continue until the conductor reaches electrostatic equilibrium, where the charges are evenly distributed across the conductor's surface and there is no net movement of charge anymore. In the case of grounding, the excess charges flow into the ground, which effectively has an infinite capacity to absorb charge, until the conductor is uncharged.
Some examples of charge movement include electrons moving through metal wires or positive and negative ions moving in ionic solutions, such as salty water.
This process of charge movement can also be observed in superconductors, which allow the movement of charge without any loss of energy, in contrast to normal conductors where electrons may collide with other particles and lose some energy.