Force on a Dielectric (5C20.20)

Description:

Dielectrophoresis due to a non-uniform electric field at the edge of a parallel plate capacitor. A circular plastic disk on the end of a pivoting arm is balanced between and slightly above the plates of a large parallel plate capacitor. As the capacitor is charged, the force on the dielectric pulls it down between the plates.

Procedure or Operation Notes:

The terminals on the Wimshurst Machine should be much closer together than shown above. Turn the handle slowly and watch the dielectric get pulled into the parallel plate capacitor. Stop turning the handle when the yellow circle sticker is inside the capacitor, and the green square sticker is still outside. The dielectric should be balanced by the force pulling it inwards and the counterweight. Discharge the Wimshurst Machine and the dielectric pivot will return to its original position.

References, Comments, or Footnotes:

1) Dielectrophoresis. [Wikipedia]

2) David J. Griffiths, "Introduction to Electrodynamics." Third Edition, 1999, Prentice Hall. See Section 4.4.4 "Forces on Dielectrics."

3) J. David Jackson, "Classical Electrodynamics." Third Edition, 1998, Wiley. See Section 4.7 "Electrostatic Energy in Dielectric Media."