Variable Gap Magnet for Physics Demonstrations Base Size_8 x 5" 8mm rod attachment and a

8mm rod attachment and a centered 50mm aperture together hold a lens square against an optical-bench rail for repeatable refraction

exposing chamber interior and septal structure for entry-level cardiac teaching

and 125mm in a plastic wallet with keepers

and the triboelectric series

this resistance box at plus-or-minus 1% on each step replaces dozens of fixed resistors at the bench

Variable Gap Magnet for Physics Demonstrations Base Size_8 x 5" 8mm rod attachment and aAdjustment screws (3 x 1 inch) on a metal base position two neodymium magnets, varying the pole gap from 0. 4 to 8. 5cm and field strength from 100 to 7500 Gauss across the working volume.