5N20.45 Tesla Coil (Large)

Description: This demo uses a larger Tesla coil to illuminate a fluorescent light bulb. The exposed components, especially the spark gap creates a loud sustained spark when operating.
The high frequency and high voltage will actually excite the gas in the fluorescent tube.


  • Large Tesla coil
  • U-Core with Yoke
  • 500 Turn Coil
  • 23,000 Turn Coil
  • Subdivided Spark Gap
  • Leyden Jar
  • Variac
  • Long florescent bulb
  • Circular florescent bulb
  • Large Clear light bulb
  • Neon gas filled tube

Setup Procedure:

  1. Connect the components according to the circuit diagram below
  2. Clear the bench of any electronics or large metallic objects

Demonstration Procedure:

  1. Turn on the variac and increase the voltage until the spark gap begins to spark (approx. 70V)
  2. Either with the lights on or off, bring one of the florescent bulbs near the Tesla coil.
  3. Repeat with the other florescent bulb.
  4. Bring one of the clear lights near it.
  5. The neon will glow red, and the light bulb will glow a purple color due to its gas composition.

High Intensity Ultraviolet Light
Do not stare at the spark gap. Dangerous amounts of UV radiation may be emitted.

High Voltage / High Frequency
Due to the high frequency high voltage, keep away from sensitive electronics.
Avoid long contact, as electrical burns may occur.