Jacobs Ladder, Science First.

The Jacob’s Ladder, or climbing arc, although perhaps best known for its role in Frankenstein movies, is a fascinating depiction of the power of static electricity. A power supply creates a powerful voltage potential (15kV) between two brass electrodes, enough to ionize the air between them and turn it into a plasma. The plasma is conductive, allowing an electric arc to form and complete the circuit. The arc dances up the electrodes, carried by rising convection currents. What makes our model so safe? Because the electrodes slant outwards, eventually the distance between them is too great to sustain the arc, which dies, only to form again at the bottom. The electrodes are shielded by a sturdy polycarbonate tube, which is extra long to prevent students from reaching into it.  A lid allows hot air to escape but prevents objects from being inserted into the tube. Each electrode is capped with ceramic to ensure the arc is extinguished, while a built-in fuse prevents overloads. The maximum current is 3 microamperes, insufficient to cause injury.  All in all, the best of both worlds - all wow, with no safety hazard.