Electricity and Magnetism > Electric Fields and Potential DCS# 5B10.40
ELECTRIC FIELD MAPPING WITH GRASS SEEDS
grass seed demo
APPARATUS
plexiglass tank 202-18-B
electrodes 202-18-B
grass seed 202-18-B
Wimshurst machine 202-18-E-1
document camera
 201

DESCRIPTION
Grass seeds in mineral oil are used to show the electric field of a dipole.

Sprinkle grass seeds uniformly around the electrodes in the tank of oil on the overhead projector.  Crank the Wimshurst and the grass seeds become polarized and line up with the electric field.  Discharge the Wimshurst before allowing students to touch the setup.




NOTES
 
To set this up, put about half a pint of mineral oil in the tank.  Secure the electrodes with the screws at the sides of the tank.  Connect the Wimshurst to the other screws using alligator clips.

Add the seeds at the last minute -- once they start to sink they are no longer very mobile.

Seeds can become charged when removed from the plastic bag, so they should be set out in the metal container.