5D40.10-Jacob’s Ladder


Video: Watch this demo

Instructor’s video

MIT Demo videp

Description: An AC power source is connected to a pair of transformers which step up the voltage.
With an initial gap of about 1cm at the bottom, ~10,000Vac creates an electric arc that rises to the top of the two metal rods.


  • VariAC
  • VariAC to banana plug cable
  • 23,000 Turn coil
  • 250 Turn coil
  • Two long metal rods
  • Iron core inductor with Iron core clamp
  • Abrasive pad

Setup Procedure:

  1. Place both coils on the inductor clamp.
  2. Attach the crossbar to the inductor and screw it on tight.
  3. Polish the metal rods with the abrasive pad.
  4. Insert the two metal rods into the 23,000 turn coil and position them to leave an air gap of about 1cm at the base.
  5. With the VariAC off, connect the cable from the VariAC to the 250 Turn coil on tap point A and E (M would half the number of turns to 125, which makes the VariAC much more sensitive (not good)).
  6. Test to make sure the spark starts and moves up the ladder.
  7. If the spark does not travel well, turn off the VariAC and adjust the rods orientation. (never adjust the rods when the VariAC is on)

Demonstration Procedure:

  1. Turn on the VariAC.
  2. Sometimes it may take 5 seconds before a spark will start. If after 10 seconds nothing happens, try increasing the voltage or decreasing the spark gap distance (with the VariAC off).
  3. Slight adjustments may be needed to the VariAC to get the spark to start and travel up the ladder.
  4. If the spark starts but stays at the very bottom, decrease the voltage on the VariAC slightly (if the spark stays too long, the metal rods will burn).
  5. Do not use for long periods of time (Over 10 minutes of continuous use).

High Voltage / High Current.
Never touch the metal rods when turned on.
Due to the high current and heat, this is fire hazard. Keep away from flammable materials.