BCIT Physics Department

Demonstration Manual

Electricity and Magnetism

DEM60 - Jacob's Ladder


- To illustrate the discharge from a large induction coil.



The air between the two rods of the apparatus becomes ionized at the point nearest each other, allowing current flow and air heating. The conducting spark will then travel up the wire pair due to heating, until a point is reached where the tapered spacing is too great to sustain the spark and the spark extinguishes. At that time, a new arc is struck at the closest-spaced location. The sequence repeats.


- Dangerous potentials exist between the two vertical conductors. (Instructor use only)