How does an electric field create velocity in a water bridge?

In summary, the phenomenon of water bridges and electrowetting involves the movement of water molecules under the influence of an electric field. This is due to the self-ionization of water, which creates ionic species that can migrate in an electric field. Additionally, other forces such as inertia, viscosity, and surface tension also play a role in the movement of water under an electric field. Further research and understanding is needed to fully comprehend the effects of electric fields on water molecules.
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HelloCthulhu
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I've been researching water bridges and electrowetting to learn the effects of electric fields on water molecules but something continues to confuse me: if polar molecules can only rotate in an electric field, how is the water moving? Anyone familiar with this phenomenon? Any help is greatly appreciated!

https://www.academia.edu/18092509/B...trohydrodynamics_of_the_floating_water_bridge
 
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  • #2
Quick guess is that the polarization places negative or positive charges closer to the source of the electric field, causing the molecules to experience a net force. Similar to the Van der Waals force between closely spaced atoms/molecules. Not sure if that's correct or not, so I hope someone with more knowledge on the topic can answer.
 
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  • #3
Water (even completely pure water) isn't just water molecules. It undergoes a process called autoionization, which very simplified looks like
$$2H_2O \rightleftharpoons OH^-+H_3O^+$$
with the caveat that these species are actually significantly more complicated than the above equation makes them seem. The point is that water self-ionizes (this is the reason that water has a pH at all), and it is these ionic species that migrate under the influence of an electric field.
 
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  • #4
I'm not sure if this will help, but this article, "Dynamics Behaviors of Droplet on Hydrophobic Surfaces Driven by Electric Field" (2019), describes in section 3. Results and Discussion that a water droplet on a substrate within an electric field is "mainly affected by the inertial force, viscous force, electric field force, surface tension and substrate adhesion". Granted the surfaces are hydrophobic, but I thought the data might still be useful since I'm interested in electrowetting as well.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6915515/
 

1. How does an electric field create a water bridge?

The creation of a water bridge through an electric field is a result of the unique properties of water. When an electric field is applied to water, the water molecules become polarized, meaning the positive and negative charges within the molecules separate and align with the direction of the electric field. This creates a dipole moment, or a separation of electrical charges, within the water molecules.

2. What causes the water molecules to move in a water bridge?

The movement of water molecules in a water bridge is a result of the interaction between the electric field and the dipole moment created in the water molecules. The electric field exerts a force on the charged particles within the water, causing them to move in the direction of the field. This results in the movement of the water molecules, creating a bridge between two surfaces.

3. How does the velocity of the water in a water bridge relate to the strength of the electric field?

The velocity of the water in a water bridge is directly proportional to the strength of the electric field. This means that as the strength of the electric field increases, the velocity of the water molecules also increases. This relationship follows the principle of electromagnetism, where a stronger electric field results in a stronger force on charged particles.

4. Why does the water bridge maintain its shape even when the electric field is turned off?

The water bridge maintains its shape even when the electric field is turned off because of the surface tension of water. Surface tension is a property of liquids that causes them to resist external forces and maintain their shape. In the case of a water bridge, the surface tension of the water molecules helps to hold the bridge together even after the electric field is removed.

5. Can the velocity of the water in a water bridge be controlled?

Yes, the velocity of the water in a water bridge can be controlled by adjusting the strength of the electric field. By increasing or decreasing the strength of the electric field, the force on the water molecules can be altered, resulting in a change in velocity. This control over the velocity of the water in a water bridge has potential applications in various fields such as microfluidics and nanotechnology.

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