5A40.70 - Kelvin Water Dropper

The Kelvin Water Drop App. can be a little touchy at times. It seems to work best if you set up the apparatus and run the water at least 12 hours in advance. You can run the water direct from the faucet and get good results but you will need the 5 gal. bucket and pump with power supply if a faucet is not available. (ie. Rm 301). You need to regulate the water flow so that the stream splits into droplets in the region of the top ring of the apparatus. This is about in the 30 volt region if using the pump.
As the charge is building up the streams will start to repel each other, eventually building up enough charge to shoot the streams outside the bottom can of the apparatus. The spacing of the spark gap will determine the amount of charge buildup. NOTE: The streams will look continuous unless you look at them with a strobe.  You can also see this effect by looking through the streams at a TV set!!  When the apparatus gets going a 1/2 inch spark every 30 to 60 seconds should be possible.
Code Number:
5A40.70
Demo Title:
Kelvin Water Dropper
Condition:
Good
Principle:
Electrostatics
Area of Study:
Electricity & Magnetism
Equipment:
Kelvin Water Drop App., 0 to 150 VDC Power Supply, Pails and Pans, Water Pump, Discharge Balls, Stroboscope.
Procedure:

The Kelvin Water Drop App. can be a little touchy at times. It seems to work best if you set up the apparatus and run the water at least 12 hours in advance. You can run the water direct from the faucet and get good results but you will need the 5 gal. bucket and pump with power supply if a faucet is not available. (ie. Rm 301). You need to regulate the water flow so that the stream splits into droplets in the region of the top ring of the apparatus. This is about in the 30 volt region if using the pump. As the charge is building up the streams will start to repel each other, eventually building up enough charge to shoot the streams outside the bottom can of the apparatus. The spacing of the spark gap will determine the amount of charge buildup.

NOTE: The streams will look continuous unless you look at them with a strobe.  You can also see this effect by looking through the streams at a TV set!!  When the apparatus gets going a 1/2 inch spark every 30 to 60 seconds should be possible.

References:
  • Se-yuen Mak, "The Kelvin Water-Drop Electrostatic Generator-An Improved Design", TPT, Vol.  35, # 9, p. 549-551, Dec. 1997.
  • Paul Chagnon, "Animated Displays VI: Electrostatic Motors and Water Dropper", TPT, Vol. 34, # 7, Oct. 1996, p. 491. 
  • Karen Brecher, "The "VideoStrobe" Water Drop Gravimeter", TPT, Vol. 28, # 2, Feb. 1990, p. 108.
  • Clifford Bettis,   "Deck the Halls: The "Ting-a-Ling" Machine",  TPT, Vol. 26, # 5, p.  340, May 1988. 
  • Michael Sady, "The Kelvin Water Dropper: An Elementary Experience", TPT, Vol. 22, # 8, Nov. 1984, p. 516 - 517.
  • William Blunk, "Kelvin Electrostatic Generator Workshop", TPT, Vol. 20, # 6, Sept. 1982, p. 412 - 413.
  • J. T. Lloyd, "Lord Kelvin Demonstrated", TPT, Vol 18, # 1, Jan. 1980, p. 16.
  • Lester Evans, J. Truman Stevens, "Kelvin Water Dropper Revisited", TPT, Vol. 15, # 9, Dec. 1977, p. 548.
  • Menno Fast, "Electrostatic Lobby Display", TPT, Vol. 10, # 2, Feb. 1972, p.100.
  • Vladimir Grubelnik, and Marko Marhl, "Drop Formation in a Falling Stream of Liquid", AJP, Vol. 73, # 5, May 2005, p. 415.
  • Gorazd Planninsic, Tomaz Prosen, "Conducting Rod on the Axis of a Charged Ring: The Kelvin Water Drop Generator", AJP, Vol. 68, # 12, p. 1084, Dec. 2000.
  • Markus Zahn, "Self-Excited AC High Voltage Generation Using Water Droplets", Vol. 41, #2, Feb. 1973, p. 196.
  • Ea-14:  Freier and Anderson, A Demonstration Handbook for Physics.
  • E-25:  Richard Manliffe Sutton, Demonstration Experiments in Physics.
  • C.L. Stong,  "Concerning Experiments with Rubber and How to Re-Create a Classical Electrostatic Generator",  The Amateur Scientist,  June, 1960.
  • Robert A. Morse, " # 5, The Kelvin Water Dropping Generator", Teaching about Electrostatics, p. 4 - 6.
  • Jearl Walker, "5.13, Danger of Spraying Water", The Flying Circus of Physics Ed. 2, p. 224.
  • 6.8, Jearl Walker, "Kelvin Water Dropper", The Flying Circus of Physics with Answers.
  • "200, Kelvin Water Dropper",  Christopher P. Jargodzki and Franklin Potter,  Mad About Physics, p. 75, 216.
  • John Vanderkooy, "An Electrostatic Experiment of Lord Kelvin with Running Water", Physics Department University of Waterloo, Waterloo, Ontario, Canada N2L 3G1. 


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