Jacob’s Ladder


If you’ve ever seen a Frankenstein movie you have probably seen a Jabcobs Ladder or “climbing arc”. The familiar “Bzzzzzzzzzzz….snap!” sound is a staple of old horror movies.

So how do they work?  First two conductive metal rods are positioned in a rough “V” shape with a slight space between them at the base.  A sufficient voltage differential is provided from a high voltage transformer to breakdown the air in the gap between the rods, at which point the electricity “jumps” the gap and creates an arc.  If there is enough electric current or amperage available, the arc will resemble a flame, and be hot enough so that convection begins to pull it upwards. As the arc rises it lengthens until it gets to a point where the rails are so far apart that it cannot sustain itself.  It then goes out and the whole process begins again at the bottom where the rods are closest together.

The Jacob’s Ladder above is powered by a 14.4kV potential transformer.  These are the types of transformers that electric utilities use to monitor line voltage.  The ladder below is powered by a 14.4kV pole transformer with higher current.  The photo was taken with a longer exposure which makes the arc look like a sheet of flame.