Member #145790

Member Since: August 7, 2010

Country: United States

  • did it in college 45 years ago and worked.

    to make it work i used;

    • a really good common ground, Stick with common point ground where called for
    • 2 941 OP amps in aliasing configuration with very high impedance input
    • used batteries ONLY not a switching supply, noise is far too high
    • electroplated copper on a 2x3 inch plastic sheet to be thin enough, Tin foil was far too thick.
    • several different magnets.
    • IMPORTANT, calibrate your scope probes
    • keep your connections short as possible
    • my Oscope was an old TechTronics made around 1962 and all vacuum tube for very high impedance.

    A bar magnet worked best due to shape of the field. Field shape and alignment will be critical.

    To get around possible induction I made an adjustable wooden holder (glue only) so the magnet would not be moving and carefully taped down all wires out to 6 inches.

    Once done the OP amp produced a steady offset proportional to the current and the distance of the magnet. Proving changing distance worked. The math from these measure followed Lorentz law as expected.

    As a secondary proof of the field to current ratio; I made a saw tooth oscillator for the current source and you could see the ramp on the scope from the OP amp output. Showing the effect of changing current. My prof really liked that idea.

No public wish lists :(