What is an electrical Jacob's Ladder?
A Jacob's Ladder is the type of high voltage "climbing arc" display seen in many old Sci-Fi movies. Jacob's Ladder come in all shapes, styles, and sizes. What is a Jacobís ladder you ask? Well, if you have ever seen any of the old Frankenstein movies or any horror movie with a laboratory in it then you have seen one. It's the funny looking device in the background that has an electrical arc rising between two eight foot steel rods over and over again giving off an eerie electrostatic sound, creating a pretty neat visual effect
The high-voltage transformer located in the pedestal wooden base creates a potential difference between the vertical wires. The electrons repel each other, so they jump from one wire to try and get as far apart as possible. The spark heats up the surrounding air and hot air rises, so the spark rises with it. When the spark gets to the top of the wires, it dies and a new one starts at the bottom.
A spark can jump between two conductors which, relative to each other, carry a high voltage. The gases in the atmosphere are pulled apart, at an atomic level, by the high electric fields generated between such conductors. The air can now conduct, just like a wire, but with a few side-effects like light and sound (thunder & lightning on a small scale).
How Does a Jacob's Ladder Work?
The simple explanation is that an arc starts at the bottom and due to the fact that hot air rises, tends to move up the diverging rods until they are too far apart for the voltage provided by the power source. While it is true that warm air pushes the arc up the ladder, there is also the typical 'high leakage' or reactance curve of the transformer contributing to the effect. Once this arc is struck the current in the arc will actually increase to the transformer's preset limit. The heat is also creating higher resistance.
The "Jacob's Ladder" toy dates back to Pilgrim times in America. This mountain toy was named after the Biblical Jacob's Ladder described in the book of Genesis (28:12). Because of the Biblical reference, Puritan children were allowed to use Jacob's Ladder as a Sunday toy.
The Jacob's ladder is one of the most ancient and famous of folk toys. Legend has it that one was found in King Tut's tomb, which means these fascinating toys were played with in Egypt before 1352 B.C., when the young king died (at about 18 years old). It's amazing to me that this humble folk toy would have been included among Tutankhamen's most significant effects, along with brilliant jewelry, amulets, masks of pure gold, prized objets d'art, a solid gold coffin, statues, furniture, and even a full-sized chariot.
Jacob's ladders, named for the biblical Jacob who saw a ladder leading from earth to heaven in a vision, have shown up all over the world. Like the spinning top, the Jacob's ladder seems to be universal, appearing at widely divergent world locations.
On December 1, 2006 a new exciting permanent exhibit was installed at the museum. The Jacob's Ladder - Climbing Electrical Arc exhibit is the largest in a USA museum at eleven feet tall and an impressive output rating of 36,650 volts. The exhibit was conceived by Richard Mathias of Hot Springs Village, AR (Vice President, MASM Board of Directors) and sponsored by Arkansas Electric Cooperatives, Inc. (Frank Bray, Transformer Design Engineer) and Rod's Pizza Cellar (Patty Roddenberry, Owner and MASM Board Member) of Hot Springs. Exhibit design was created by Niles Ellis, MASM Deputy Director and constructed by Kenn Beaver, Exhibit Fabricator and Ken Ewing, Volunteer Mechanic of Hot Springs Village, AR.