Building bridges, i.e., bridge circuits is an involving and thought-provoking way to determine the resistance in an unknown wire. This classic experimental device compares a wire with known resistance to a wire with an unknown resistance and then uses a simple mathematical formula to determine the unknown resistance. You need a galvanometer to indicate the exact spot on the slide-wire device when the current ceases to flow and the bridge is balanced. Resistance coil (AP5701) and resistance board (AP5702) are ideal sources for unknowns for your experiments. Unit comes assembled with detailed directions and background.