5B20.XX Flux Model


Electric/magnetic flux through a closed loop as a function of angle


The model shows how the flux ('number' of field lines) through a closed loop changes as the angle between the field lines and the loop changes. The relation between flux and angle may be quantitatively determined if desired.



  • [1] Flux model made from a 10 x 10 grid of nails
  • [1] Square wire loop


  1. Place the loop on the nail grid at a variety of angles to show that the number of field lines (nails) through the loop changes with angle.
  2. If it's a small class, pass around the demo.


Additional Resources


  • PIRA 5B20.XX


  • Don't attempt this at home!

Last revised

  • 2020


  • Original construction: the 'field lines' were made from 3.5" bright finishing nails hammered into a predrilled 10 x 10 grid with a .2125" spacing. The base of the nail 'field line' model is a block of 3.5" x 3.5" x 0.75" wood. The square wire loop was made from 16 gauge copper wire wound in a single turn around the nail grid to form an approximately 2.5" x 2.5" square loop. The loop was soldered closed for robustness.

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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.