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Tesla Coil Experiments

A homemade Tesla Coil is great for special effects style science experiments. The high voltage, high frequency output can cause strange effects in all sorts of materials. The Tesla Coil used in these experiments has a pipe inside the centre of the secondary coil. This pipe allows gas to be emitted from a small hole in the topload sphere.

Electricity and Fire

Fire is a type of plasma, as the constant exchange of electronic bonds between the molecules and the release of energy allows electrons to move around under the influence of an external electric field. Fire is considered as a 'cold plasma' because it temperature is relatively low when compared to electrically generated plasmas. A small flame from butane gas emitted form the top of the Tesla Coil acts as a discharge terminal or breakout point. The hot gasses rising from the flame also provide a further conductive channel.

Tesla Coul and Small FlameTesla Coul and Small FlameTesla Coul and Jet Flame

These images show how the electrical hot plasma from the Tesla Coil blends with the cold plasma of the flame. Click on the photos for a full view.

The rightmost image shows the electrical discharge through a hot jet flame like that of a bunsen burner. This flame causes the arc to stay mostly in one filament until the turbulence becomes too great.
See more photos of plasma on the plasma page





Noble Gases

The Noble gasses (often refered to as inert gas) are often used to make plasma because they will not react with the electrodes or surrounding material. Different gas types have different ionization voltages, and will also emit different colours of light.

Tesla Coil and Neon GasTesla Coil and Neon GasTesla Coil and Neon Gas

These photos show what happens when pure Neon gas is emitted from the top sphere of a small Tesla Coil. Neon has a much lower ionization voltage than air, so the gas will glow very brightly creating a plasma column to allow the arcs to be much larger. The picture on the right looks similar to the 'death ray' devices used in the movie War of the Worlds! You can see when tuned correctly the individual filaments tend to form multiple helices, allowing the plasma column to rise quite high.
See more photos of plasma on the plasma page

We can see from these images that the Neon only helps to increase the length of the plasma filaments when it is still relatively concentrated. The neon is not 'burnt' or consumed, but it quickly mixes with the air, and its effects on the plasma become negligible.

The top left video clip shows a TC with a perspex hemisphere loosely covering the top. When Neon gas is emitted from the top sphere it is forced to spread over the surface before escaping. You can see how the neon layer glows red. The next clip of a spontaneous single filament shows the TC in normal operation.

The erratic flowing arcs spontaneously disappear then return as one single extra long arc. The last two clips show how the gas affects the TC when it is emitted directly from the top of the metal sphere

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