What makes a Kelvin Generator work?

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SUMMARY

The Kelvin water dropper operates by utilizing the principles of charge separation and electrostatic induction. As water drips from the apparatus, it creates a positive charge on one side and a negative charge on the other, leading to a buildup of electrical potential. This charge accumulation occurs due to the presence of ions in the water, which can be influenced by friction during the drop formation. The process ultimately results in the generation of sparks when the potential difference becomes sufficiently high.

PREREQUISITES
  • Understanding of electrostatics and charge separation
  • Familiarity with the concept of ions in solutions
  • Knowledge of friction and its effects on charge transfer
  • Basic principles of electrical potential and spark generation
NEXT STEPS
  • Research the principles of electrostatic induction in detail
  • Explore the role of ions in water and their effect on electrical conductivity
  • Study the physics of friction and its impact on charge generation
  • Investigate practical applications of the Kelvin water dropper in educational demonstrations
USEFUL FOR

Students of physics, educators demonstrating electrostatic principles, and hobbyists interested in electrical experiments.

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I am wondering how a Kelvin water dropper works and can generate sparks. Basically, water drips onto two sides, and the apparatus attracts positive charge to one side and negative charge to another side. The charge eventually builds up high enough to make a spark. You can see more information about it here:
http://en.wikipedia.org/wiki/Kelvin_water_dropper

I can understand that general idea, but what I don't understand is where the positive and negative charge comes from. Isn't a single water molecule neutral? It would have (1 + 1 + 8 = 10) protons and also 10 electrons, so the net charge of a single molecule would be 0... So what would be making the buildup of charge?
 
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Everything is explained in the wiki page you linked to, hard to add something to the description given there. Molecule of water is neutral, but solution is full of ions - single drop is neutral only on average, as it can easily contain few cations or few anions more. Then when the drop is created and falls it can get additionally charged due to friction.

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