Attraction of water droplet to my finger?

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    Attraction Water
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Discussion Overview

The discussion revolves around the physical explanation for the phenomenon of water droplets being attracted to a dry finger after rain. Participants explore concepts related to adhesion, molecular polarity, and the effects of moisture on the interaction.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant describes the observation of water droplets jumping to a dry finger and questions the physical explanation behind it, suggesting the role of induced dipoles.
  • Another participant identifies the phenomenon as adhesion and proposes that induced dipole interactions may be involved.
  • Some participants argue that the negative polarity of the oxygen end of water molecules attracts to the positively charged finger, emphasizing the role of molecular polarity.
  • It is noted that if the finger is slightly wet, the interaction may also involve hydrogen bonding and ionic compounds present in sweat, contributing to both cohesion and adhesion.

Areas of Agreement / Disagreement

Participants express varying perspectives on the mechanisms involved, with some agreeing on the role of molecular polarity while others introduce additional factors like moisture and ionic compounds. The discussion remains unresolved regarding the precise contributions of each factor.

Contextual Notes

Participants do not fully explore the assumptions behind their claims, and the discussion lacks a detailed examination of the underlying physical principles governing adhesion and molecular interactions.

pivoxa15
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After a rain, when there are tiny water droplets hanging down from places, I can put my dry finger near one of the droplets and if my finger is close enough to the droplet, it will jump onto my finger. Just like a metal jumping onto a magnet.

What physical explanation could be given here? Is it simply the negative ends of all the water molecules in the droplet attracted to my positively induced finger?
 
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i think you hit it, negative polarity on the oxygen end of water attracts to your positively charged finger.

if you're finger was slightly wet though it would have been due partly to the polarity of the molecules and partly due to hydrogen bonding
 
rctrackstar2007 said:
i think you hit it, negative polarity on the oxygen end of water attracts to your positively charged finger.

if you're finger was slightly wet though it would have been due partly to the polarity of the molecules and partly due to hydrogen bonding

This is indeed a good point, sweat contains not only the polar H2O water molecule, but also ionic compounds, which could contribute to the effect. If your finger is damp / sweaty you will have both cohesion and adhesion.

~H
 

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