The Plasma Globe offers you a safe, fascinating way to demonstrate how lightning works as well as explain the concepts of potential differences and electron orbital jumping.
The plasma globe consists of a partially evacuated glass sphere containing a mixture of gases at fairly low pressure. The smaller sphere at the center of the glass sphere is connected to a small Tesla coil (high voltage, high frequency, yet low current source of alternating current) produces a large potential difference between it and the glass of the surrounding globe, similar to a cloud and its potential difference with the ground. This potential difference uses inert gases inside the globe to complete a circuit and release its potential to the outer glass, just as a cloud releases its potential to the ground. The result? Bright, harmless, violet "lightning bolts" that respond to touch and sound. Touching the glass side will cause a plasma stream to flow to your finger tips. Bring a fluorescent tube close by and the high voltage will light it.