Jacob's Ladder-Climbing Arc (Carol Cao)

Author

Carol Cao, Summit View School

Principles

electrical arcs, air conductivity, Paschen's Law

Standards

Electric and Magnetic Phenomena

  1. Electric and magnetic phenomena are related and have many practical applications. As a basis for understanding this concept.
    1. Students know charged particles are sources of electric fields and are subject to the forces of the electric fields from other charges.
    2. Students know magnetic materials and electric currents (moving electric charges) are sources of magnetic fields and are subject to forces arising from the magnetic fields of other sources.
    3. Students know how to determine the direction of a magnetic field produced by a current flowing in a straight wire or in a coil.Students know plasmas, the fourth state of matter, contain ions or free electrons or both and conduct electricity.
    4. * Students know electric and magnetic fields contain energy and act as vector force fields.

Materials needed

Electrical Source, a Jacob's ladder device. See References to find out how to make one.

Procedure

Once you have obtained a Jacob's ladder or made one yourself, make sure the wires are enclosed in a tube to help keep air drafts from affecting the results. Apply the power source and watch the arc form. 

Explanation

The Jacob's ladder produces a continuous electrical spark/arc that rises up from the bottom of the device. There is a gap between the two wires extending from the base of the device.  The two wires from a narrow "V" shape. When voltage is given to the gap, a spark forms at the bottom of the wires where the gap is narrowest. This spark quickly changes to an electrical arc. The arc takes in much of the electrical supply and the voltage across the gap is reduced.  As air heats up around the arc, the air rises carrying the electrical current up the ladder. As the arc moves up, the distance between the two wires increases.  The arc becomes more and more unstable and will eventually break.  The voltage across the bottom of the device and electrode begins to rise again forming another spark. 

Questions
  1. Inculde at least three questons (with answers) that you can ask to assess understanding of the principles ilustrated
  2. Question
  3. Question

Everyday examples of the principles illustrated

spark plugs, electrostatic machines, x-ray machines, microwave oven transformers, 

Photos


Movies

Jacob's Ladder-Climbing Arc

References

Spark Gaps

          Climbing Arc-How to make one


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