Electricity and Magnetism > Electric Fields and Potential

DCS# 5B10.40

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ELECTRIC FIELD MAPPING WITH GRASS SEEDS

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APPARATUS

plexiglass tank	202-18-B
electrodes	202-18-B
grass seed	202-18-B
Wimshurst machine	202-18-E-1
document camera	201

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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 document camera. Crank the Wimshurst machine and the grass seeds will become polarized and align with the electric field.  Discharge the Wimshurst before allowing students to touch the setup.

NOTES

 

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.