15 gold plated neodymium spheres are arranged in a straight line then rolled down an aluminum ramp.

Interconnected coils are hung as pendula in the gaps of two horseshoe magnets. Start one swinging and the other swings.

An relaxation oscillator is made with a resistor, capacitor, and a neon lamp.

Consist of an array of loosely confined metal pins in a clear plastic case. To be used in conjunctions with a overhead projector