Preparation of graphite conductive paint and its application to the construction of RC circuits on paper

Abstract

We describe a simple procedure for the preparation of graphite-based conductive paint and determine its basic transport properties when applied, comparing them to those of pencil strokes. Ohm’s law was fulfilled on the applied paint, which makes it an ideal strategy to teach the relations between a resistor’s length, width and resistance. The conductive paint was used in the construction of RC circuits on paper in a simple and didactic format. Using only the paint and a piece of cardboard, a completely functional parallel plate capacitor can be constructed with different plate geometries; in particular, we painted circular and rectangular plates. The charge and discharge cycles of the two RC circuits painted were observed in the oscilloscope. We obtained characteristic times and estimated the value of the dielectric constant of paper, which serves as a dielectric between the plates of the capacitors. We found conductive paint to be a useful and easy method to teach basic electricity and circuit concepts in fundamental courses and lab practices because it allows one to visualise properties such as the dependence of resistance and capacitance with geometric factors using a specific material.