Overbeck Electric Field Mapping Apparatus

This highly accurate apparatus uses the null method to find equipotentials.

The equipotential lines of an electric field define its size and shape. Experiments with this apparatus are based on the field-mapping board, which has two thumbscrews on the underside for fastening on conducting field plates. Six of these plates are included. Five have the following popular patterns permanently printed with conductive paint: a parallel-plate capacitor, an insulator and conductor within a field, two point sources within a field, a point and plane, and the Faraday Ice Pail. The sixth plate is blank, so you can paint your own design in conductive silver paint. The set also includes two templates.

To use the apparatus, attach one of the plates to the bottom of the mapping board with graph paper over the top. A potential divider with eight equal resistors is connected to the board, which has seven banana jacks along its top surface. To plot a point on an equipotential line, cover the board with graph paper and slip the long U-shaped probe around the board. With the probe and galvanometer connected to one of the seven potential jacks, a new reading is found at all points on the equipotential. You can mark the paper through a hole in the probe. Plotting and connecting these points for each of the banana jacks gives an excellent picture of the equipotential lines.