![Break Down of Air (D29) [5A50.30] @MITPIRL](https://i.ytimg.com/vi/ynngFTTIA2I/maxresdefault.jpg)
Uploaded June 2012 | Updated September 2026, 2 weeks ago
Grounding rod tips of different sizes are used to discharge a large Van de Graaff generator. The larger the curvature of the tip, the more charge must build up to break down the air, resulting in longer sparks. The electricity ionizes air molecules, releasing quick flashes of light.
A pointed tip barely sparks at all, but instead creates an electric field so strong that it forms a tiny ball of plasma just beyond the tip. This is known as "St. Elmo's Fire", and is just visible when all the lights are turned off.
Grounding rod tips of different sizes are used to discharge a large Van de Graaff generator. The larger the curvature of the tip, the more charge must build up to break down the air, resulting in longer sparks. The electricity ionizes air molecules, releasing quick flashes of light.
A pointed tip barely sparks at all, but instead creates an electric field so strong that it forms a tiny ball of plasma just beyond the tip. This is known as "St. Elmo's Fire", and is just visible when all the lights are turned off.
![Break Down of Air (D29) [5A50.30]](https://i.ytimg.com/vi/ynngFTTIA2I/mqdefault.jpg "Break Down of Air (D29) [5A50.30]
Grounding rod tips of different sizes are used to discharge a large Van de Graaff generator. The larger the curvature of the tip, the more charge must build up to break down the air, resulting in longer sparks. The electricity ionizes air molecules, releasing quick flashes of light.
A pointed tip barely sparks at all, but instead creates an electric field so strong that it forms a tiny ball of plasma just beyond the tip. This is known as St. Elmos Fire, and is just visible when all the lights are turned off.")
![Coupled Air Carts (C20) [3A75.10]](https://i.ytimg.com/vi/zlzns5PjmJ4/mqdefault.jpg "Coupled Air Carts (C20) [3A75.10]
Two or more air carts are connected by springs on an air track. When this system is at resonant frequency, symmetrical patterns called normal modes appear. The normal modes are shown in both undriven and driven cases. In the undriven examples, the normal modes are found by placing the carts at certain distances from each other and then letting them oscillate. In the driven examples they are found by driving the system with a motor, and varying the frequency until the normal mode patterns appear. Both of these methods are shown for systems of two, three, and five coupled carts.")
