Concepts

Ionization of noble gas, corona discharge, electric glow discharge, plasma

Overview

A plasma globe consists of a glass sphere with an electrode in the center of the sphere and it is filled with various noble gases. Ionization of gaseous particles occurs when free electrons collide with the gaseous atoms inside the globe, creating electrons and positive ions. When electrons return to the ionized gas, light is produced. Placing a conductor or fluorescent light on the glass creates an attractive spot for the energy to flow because it is more easily polarized and serves as alternative path of less resistance. Note: not all demos done with this apparatus are visible in a large classroom.

Details

Equipment

• [1] Plasma globe
• [1] Fluorescent tube
• [2] Coin
• [1] Step stool

Classroom Assembly

1. Place the plasma globe on a horizontal surface near a power source.

Script

1. Turn on the plasma globe.
2. Place the first coin on top of the globe and bring the second coin to a close proximity to the first coin.
3. When the two coins are close enough, notice an electrical spark is created between the two coins.
4. Place a fluorescent tube on top of the globe, notice the tube lights up upon contact with the plasma globe.
5. Get a student volunteer to help with the next experiment.
6. Ask a student volunteer to stand on top of the stool and place one's hand on top of the plasma globe while holding the fluorescent light with the other hand.
7. Touch the tube starting close to the volunteer's hand and slowly slide along the tube away from the hand. The tube should increasingly light up as you move your hand.

Additional Resources