Prev. Article Next Article Table of Contents

Article

Electrical Deflection of Polar Liquid Streams: A Misunderstood Demonstration

Your current credentials do not allow retrieval of the full text.

Purchase the full-text

PDF/HTML,
figures/images,
references and tables,
(where available)

Maryam Ziaei-Moayyed and Edward Goodman

Honors College, Arizona State University, Tempe, AZ 85287-1604

Peter Williams

Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604

J. Chem. Educ., 2000, 77 (11), p 1520

DOI: 10.1021/ed077p1520

Publication Date (Web): November 1, 2000

Section:

History, Education, and Documentation

Abstract

The electrical deflection of polar liquid streams, commonly used as a textbook illustration of the behavior of polar molecules, is shown to be due to the formation of electrically charged droplets in the polar liquid stream, induced by a nearby charged object, rather than any force exerted on molecular dipoles. Streams of water and polar organic liquids could be deflected in a uniform electric field, which could not have exerted any force on dipolar species. Water and polar organic liquid streams formed within a grounded, electrically screened region could not be deflected after exiting the screened region, demonstrating that there is no electrical force on uncharged polar liquid droplets. Induced charging was observed also in insulating polar organic liquids and is suggested to be due to ionic impurities. A weak deflection of a stream of a nonpolar liquid (tetrachloroethylene) was also observed, indicating that such impurity effects are quite general, even in nonpolar liquids.