In the last couple of years, I have made good use of the “bare wire” lab for electric potential difference. I first learned a version of this lab in the Modeling curriculum for electricity and magnetism. In this activity, students measure the potential difference of bare wires connected to a battery pack, but not connected to anything else.

This is extremely helpful in developing the idea that a wire can have zero potential difference along its length. And in developing the idea of potential difference being a difference between two different points.

Then, students connect a long bulb and a round bulb to the battery and repeat their measurements.

Finally, they make a graph of potential versus position.