Here is a rare attempt to describe how, over the course of more than a century, our understanding of electricity and magnetism slowly developed (published by the electrical engineering professional society). But even this account gets ahead of itself by invoking concepts and information that did not exist at the time (such as the much later discovery of electrons):
The Long Road to Maxwell's Equations, IEEE Spectrum, December 2014 (link / cached copy)
YouTube movies of pith ball demonstrations:
Quick looks (un-narrated, but one using live cat fur):
My "Virtual Lab" computer animated explanations of Pith Ball experiments
Exploiting the powers of virtual reality to "see" invisible / microscopic charge movement
Snapshots from "Pith Ball Basics" (LINK to full X-ray vision animation):
Snapshots from "Pith Ball Ping Pong" (LINK to full X-ray vision animation):
My classroom demonstrations:
1) The effect of magnets upon metals:
Do magnets attract ALL metals?
Demonstrating the importance of containing iron (or iron-like metals = "ferromagnetics").
But also how, despite containing 98-99% iron, the magnetism of steels
be extinguished by adding certain trace metals.
2) The effect of magnets upon magnets, compasses & iron filings:
Yielding "Magnetic Fields" which, unlike Electric Fields, do NOT map forces!
This "3D Magnetic Field Demonstrator" was purchased from Pasco Scientific (www.pasco.com - P/N SE-8603)
3) The effect of electrical current upon a compass:
Oersted's lecture hall accident - and Ampere's explanation thereof.
An entirely home-built demonstration.
4 & 5) Magnetic vs. non-magnetic balls falling through long copper pipes:
A recipe for defying gravity?
Single Copper Pipe:
Copper Pipe + Plastic Pipe on a Spring Balance:
This "Lenz Law Apparatus" was purchased from American Scientific (www.american-scientific.com - P/N AR-105)
This "Lenz Law" apparatus was purchased from The Science Source (www.thesciencesource.com - P/N 32520)
6 & 7) A long cylindrical magnet falling through short copper pipe:
Which parts of the magnet slow its fall?
Explanation of the apparatus:
Drop Tests 1 & 2 (at full speed & half speed):
Calculated magnet velocity in Drop Test 1:
Calculated magnet velocity in Drop Test 2:
- Original high resolution 60 fps Quicktime movies providing times & frame numbers (links for Drop Test 1 / Drop Test 2)
- Excel spreadsheet with raw data for both tests + finite difference calculation of velocities & accelerations (link)
This home-built apparatus used four 2.5 cm long x 1.25 cm diameter neodymium rare earth magnets purchased from Indigo Instruments (indigoinstruments.com - P/N 44204-25), a 5 cm long 1/2" I.D. x 1" O.D. copper pipe (machined from solid copper rod), and a 5 cm long x 1.25 cm diameter plastic guide rod (with a small iron washer attached to one end by a brass screw)
8) HOW Magnetic InductionPLUSElectro-magnetismALMOST defied gravity:
The current meter used has a +/- 250 micro-Ampere range, and is available through Amazon.com at this link.
9) The effect of moving magnets upon "non-magnetic" aluminum shapes:
The basis of technologies ranging from "brushless motors" to magnetically levitated trains!
This apparatus combines the "Magnetic Force Accessory" & "Variable Gap Magnet" from Pasco Scientific (www.pasco.com - P/N EM-8642A & EM-8618).
The railcar / rail assembly is a"video camera slider" purchased from B&H.com
We Can Figure This Out. Org's movie studio (a.k.a., my basement wood/metal shop):
The use of magnetic induction to sort non-magnetic metals: