Pictures
Here are some good pictures of arcs and sparks from some high voltage devices that are on this page. This page is becoming the largest on the site, so I decided to index it.
This arc is from the 15-40kV ignition coil driver device. I used two ignition coils rather than just one. The "+" terminal on one coil is connected to the "-" terminal on the other coil and vice-versa. This connects their primaries in parallel and their secondaries in series. The arc can reach out with about 3" at times. This picture shows a continuous arc around 30-40kV which is about 2" long but can be spread out even further. This is a great circuit for powering a Jacob's ladder. The reason why the arc tends to look like an upside-down "vee" shape is caused by the hot air rising.
These are sparks created by the 15-40kV ignition coil device. The sparks are about 2 1/2" in length. Again two ignition coils connected in series (secondaries) for more voltage is used to obtain longer sparks. The potentiometers also need to be adjusted to produce sparks.
This picture shows just one spark. It looks purple but it's actually blue. It is about 2 1/2" long.
This picture is of a large group of sparks. When I recorded this the light from the sparks "blended" together, so it's looks like an arc but it's actually many sparks. Length is about 2 1/2".
This picture is a running Jacob's ladder using the 15-40kV ignition coil device. The arc is very hot and will travel all the way up the ladder almost every time.
The first picture is of the arc in the center as is the second picture. The third picture is of the arc at the top almost ready to be drawn out too far and extinguished. The rods used for this ladder are about 2' 6" long.
These three pictures are of a far more incredible Jacob's ladder. It uses one microwave transformer. Voltage is approximately 2100-2400Vrms at 500mA! Arcs on the ladder got to be nearly 6" wide. Unfortunetely the arc on the ladder has to be started by hand (no don't use your hand!), sometimes however, it started itself and rose up the rails. If you build one of these, make sure to secure the ladder well (you don't want it to fall on you during operation!) and definetely put a power-factor correction capacitor in parallel with the primary. A normal Jacob's ladder can be made by using two or more of these in series.
This is a picture of a Jacob's ladder which uses a 15kV neon sign transformer. The current is 30mA. A neat thing to do with a Jacob's ladder is to put salt on the rails. This will make the arc turn bright orange. The picture isn't too great, someday I will redo all the bad ones with my Snappy.
More to come soon. Flyback arcs, gas discharge tube, more Jacob's ladders, plasma globe, etc.