You will need the following:
- Neon transformer or a oil burner transformer (at least 5KV).
- Heavy-duty grounded plug/cord. Cords from computers work nicely.
- 8 to 12 gauge copper wire. Clothes hangers work nicely when the paint is removed.
- Wood for the base and frame.
I used a 12KV 60mA neon transformer, which is easily capable of making a nice white arc. The rods start at about 1/4 - 1/2 inch at the bottom and end at 2 - 3 inches on the top. Microwave oven transformers are not recommended because most provide 2.5KV at 500mA; the voltage is too low to start an arc easily and the current is rather high. I had some luck with using neon transformers at around 5KV, but starting and sustaining an arc is difficult. A 1Meg resistor has to be connected to one of the rods and the other end of the resistor is placed between the rods at the bottom to help start the arc. The rods cannot spread out over an inch with transformers below 9KV or the arc will extinguish prematurely. Below is a basic schematic diagram of the circuit.
The arc will begin at the bottom of the rods where air resistance is lowest. The arc generates heat that lifts the arc up until it extinguishes, then a new arc ignites at the bottom. The arc is basically plasma where oxygen (O2) is converted to ozone (O3).
Close-up of the wood frame & transformer.
Arcs from my Jacob's Ladder.
Below is my second Jacob's ladder using an older-looking transformer that provides about 5KV. Note the use of the Gabriel gap (1Meg resistor between the rods) to help start the arc.