School of Physics Lecture Demonstration Manual

Ec-2 Jacob's Ladder

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011


To demonstrate that an electric arc discharge will rise with the convection current it creates.



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Jacob's Ladder Diagram


Jacob's ladder consists of two horn shaped electrodes connected to a large induction coil. The coil operates from 12 Volts D.C. On closing the switch K a spark strikes at the lower end and climbs to the top where the distance between the electrodes is considerably greater. The spark rises with the convection currents due to the heat from the source.

Safety notes

Electrical safety 


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