Play-Doh Resistors: Lessons from 2-wire and 4-wire DC and AC data

Some high schools and universities use Play-Doh as a resistor in introductory electricity labs. By using Play-Doh, students verify Ohm’s Law and explore resistivity using familiar rulers and a pleasant tactile experience. Published examples of this experiment simplify the analysis by using 4-wire measurements; but these mask effects prominent in Play-Doh but absent in ideal metal wires.

We performed DC and AC measurements of current and voltage through carbon electrodes into Play-Doh cylinders. Our results reveal changes in the bulk of the Play-Doh, as well as interfacial capacitance. Discussing these effects in introductory physics classes enables discussions about real vs. ideal conductors, measurement limits, and new technologies.