The effect of an electric force on the fall speed of a particle has been considered using a simple model of a spherical particle of radius r in a vertical electric field E, with weight W, an Archimedean upthrust U, an electric force FE, and a drag force FD. If the particle is moving downward but experiencing an upward electric force (due to carrying a negative charge in a downward-directed field, such as that in fair weather), then the balance of forces in equilibrium can be represented asEmbedded Image(4)

The ratio of U to W is given by the ratio of the densities of air ρa and the particle ρp, which is ~1:1000; hence, U<<W and U can be neglected. The drag force depends on the particle’s projected area A (= πr2), its fluid-relative speed v, and the drag coefficient CD. Assuming a spherical particle carrying a charge q, the electric force can be written as qE, the drag force parameterized as Embedded Image; hence, the equilibrium description of Eq. 4 becomesEmbedded Image(5)

For calculation of v, CD depends on the flow and the associated Reynolds number and typically varies from 0.5 to 1.5 for a smooth sphere.

Note: The content above has been extracted from a research article, so it may not display correctly.



Q&A
Please log in to submit your questions online.
Your question will be posted on the Bio-101 website. We will send your questions to the authors of this protocol and Bio-protocol community members who are experienced with this method. you will be informed using the email address associated with your Bio-protocol account.



We use cookies on this site to enhance your user experience. By using our website, you are agreeing to allow the storage of cookies on your computer.