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Steve-o Stonebraker

For my students I threw together a simulation to illustrate field cancelation inside a spherical shell, a la Newton's "shell theorem".

For visual simplicity this is 2D only! It uses a ring and 1/r force rule as an *analogy* for a spherical shell in our 3D universe with a 1/r^2 force.

As you increase the number of particles in the ring, the results approach the theoretical limit as described by the shell theorem with a zero net field on the interior.

desmos.com/calculator/5huw6ylq

You can also toggle the force rule to a 3D 1/r^2 version if you want, and will see that the net field inside the ring is no longer zero. You would need a full spherical shell--not a 2D ring--to get zero field from a 1/r^2 force.

I hope other folks find this useful!

Let me know if you have feedback or suggestions. :)