Young professor teaching class at the university

Tesla coil and gas tubes. Footage of a Tesla coil producing high-voltage electrical sparks (top centre), with the purple glow caused by ionisation of air molecules to form a plasma. The strong electric fields created by the Tesla coil cause the gases in discharge tubes to glow. Several examples of this are shown here: first a neon gas tube (orange glow), then a krypton gas tube (purple glow), then a nitrogen gas tube (red glow). The discharge in the nitrogen gas tube is shown being manipulated by touching the glass and moving a finger up and down the tube.

Teenage girl writing exam while teacher guiding her in classroom at high school

High-voltage electricity and soot on a glass slide. Footage of a glass slide being blackened with candle soot, and then connected in a circuit with a high-voltage generator. The high voltage causes electrical sparks to burn patterns in the carbon on the glass slide, showing the path taken by the electricity.

Lightning flask experiment. Footage of a high-voltage generator (right) being used to generate plasma discharges from a metal plate (lower left) to a round-bottomed flask (left) containing an electrolyte (salt) solution. The metal plate is placed under the flask and covered with a sheet of white paper. Electric arcs are visible with the lights on, and then in close-up with the lights off. The purple glow is due to ionisation of air molecules to form a plasma.

Rear view of students spread out across a lecture hall, at the front facing them and standing at the lectern is their professor

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High-voltage electricity damaging a light bulb. Footage of a high-voltage generator (right) being used to generate electrical sparks in a light bulb (left) using a wire cap. This display of purple electrical sparks is shown in close-up with the lights off. This display of purple electrical sparks is due to ionisation of the gas inside the bulb, forming a plasma. The high voltage eventually damages the glass, shown by the plasma disappearing to be replaced by a single continuous yellow spark and flame. The lights are turned back on and the power turned off. The demonstrator then turns the light bulb to show the small hole burnt through the glass of the light bulb.

High-voltage electricity destroying a CD-ROM. Footage of a high-voltage generator (left) connected in a circuit with a read-only-memory compact disc (CD-ROM, right), with the high-voltage electricity destroying the CD-ROM. The sparks are melting and removing the aluminium on the disc, erasing any data it held.

High angle view on School Children Studying in Education Library

High-voltage electricity and a light bulb. Footage of a high-voltage generator (right) being used to establish a circuit with a light bulb (left). The high voltage causes electrical sparks to jump across the gap between the crocodile clip and the light bulb. This display of purple electrical sparks is due to ionisation of the gas inside the bulb, forming a plasma. This is shown here with the lights on and then in close-up with the lights off.

Row of high school students sitting at desks in classroom using their phones with paper assignments in front of them

Two Girl Students in Science Class Looking at a Molecular model Together

High-voltage generator and electric discharges. Footage of a high-voltage generator being switched on to produce electrical discharges across a spark gap (upper centre). With the lights turned off and on during the clip, the electric arc discharges are seen in close-up as they ionise the gas molecules to produce a glowing plasma (purple). This generator is capable of producing voltages of up to 50,000 volts.

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High-voltage discharges and inorganic salts. Footage of a high-voltage generator being used to produce electrical discharges onto various inorganic salts, with the colour of the resulting glows depending on the chemical composition of the salts. The inorganic salts are placed on a piece of aluminium foil. The normal colour of the sparking electric arcs is purple, resulting from ionisation of molecules in the air. The first inorganic salt to be subjected to the high-voltage discharges is calcium chloride, resulting in a red-orange glow. This is followed by a green glow from magnesium chloride, and a yellow glow from barium chloride.