Physics Dept. Demonstration Manual

DEM29 - Magnetic Field About a Solenoid


To show the direction and the pattern of the magnetic field about a current-carrying solenoid.

  • Coil mounted on a projection board
  • Iron filings
  • Compass (OHP)
  • Power supply, 30 amp, 1 volt (Twel)
  • Heavy leads (2 spade-spade)
  • Sheet of white paper (if not using the overhead projector)


The coil unit is focussed on the overhead projector by placing a compass on its surface and adjusting the focus head. Once the focus is established, and the power switched on, iron filings may be sprinkled in the area of the wire to show the magnetic field pattern. The direction of the magnetic field may be shown by moving a (OHP) compass on the inside and around the coil.

If you are not using the Overhead Projector then place a piece of white printer paper under the apparatus.
You will be able to see the pattern created by the iron filings much better.


Tap the unit when sprinkling iron filings. This produces a clearer pattern analogous to the field pattern of a bar magnet.