The circuit diagram of an ideal solar panel is shown in Fig. 1. Presumably, the devices are wired in series to reduce I2R resistive losses.1 For our study, we used a Sharp 240-Watt MultiPurpose Module (part # NU-Q240F2) solar panel mounted on a horizontal pivot behind the central axis of the panel frame to facilitate variation of tilt (see Fig. 2). The present cost for a typical commercial module like this is a few hundred dollars. We connect the electrical output of the panel to a low-resistance, high-current sliding rheostat (rated 15.2 ohms and 8.5 A, manufactured by the James G. Biddle Co.) to accommodate measurements of current and voltage as a function of load. A quick Internet search indicates that a comparable rheostat can be purchased (used) on eBay for about $50.