Electricity!
This display allowed the visitor to create simple electrical circuits using modules. An extensive technical treatment can be seen here.
See the slide show below for an explanation of the exhibit.
The visitor can use the large knob in the center of the display to select between 3, 6, or 9 volts. Seen here, the selector is set to 9 volts.
In this close up, the yellow module, which contains a small incandescent bulb, is attached to the two white modules which contain simple wires. In this way, circuits can be made with various components.
This green module contains a small motor. A direction indicator is provided to show that the motor will change direction depending on its orientation in the circuit.
This module contains a buzzer.
This module contains two LEDs. They are arranged with opposite polarities so that the green LED will light in one direction, and the yellow will light if the module is flipped in the circuit.