In this simulation, you can investigate the electric field and the electric potential at various positions along a line, when there are either one or two charged particles on that line. In particular, you can explore the connection between the field and the potential.
The field and potential are represented in two ways. First, the table at the bottom shows the values of the electric field and electric potential at the position of the point charge. Values are given for the field and potential due to each charged particle individually, as well the net values.
The second way to represent the field and potential is graphically. You can look at both the graph of the electric field as a function of position, as well as the graph of the electric potential as a function of position. The graphs are probably most helpful in determining how field and potential are connected.
In addition, the arrows attached to the movable test charge show the field at the position of the test charge from the two charged particles.