Jacob's Ladder

The blue streaks of electricity smoothly sliding up the antennae extensions sends sizzling chills up your spine and causes your skin to squeeze itself into an almost acid-like intensity. You stand absolutely still, not knowing if the next move might cause this unpredictable power to advance upon your fragile frame and induce an afterglow upon your head. A Jacob's ladder (more formally, a high voltage traveling arc) is a device for producing a continuous train of large sparks which rise upwards. The spark gap is formed by two wires, approximately vertical but gradually diverging away from each other towards the top in a narrow "V" shape. It was named for the "ladder to heaven" described in the Bible. When high voltage is applied to the gap, a spark forms across the bottom of the wires where they are nearest each other, rapidly changing to an electric arc. Air breaks down at about 30 kV/cm, depending on humidity, temperature, etc. Apart from the anode and cathode voltage drops, the arc behaves almost as a short circuit, drawing as much current as the electrical power supply can deliver, and the heavy load dramatically reduces the voltage across the gap. The heated, ionized air rises, carrying the current path with it. As the trail of ionization gets longer, it becomes more and more unstable, finally breaking. The voltage across the electrodes then rises and the spark re-forms at the bottom of the device.