1. Attach an appropriate current source to the magnetic field viewer with patch cords. MAKE CERTAIN THAT YOUR CURRENT SOURCE IS INTERNALLY LIMITED!! Since the wire coil has a very low resistance, it will appear as a short circuit to an external power supply. An external ballast resistor may be necessary, depending on the power supply you use.
2. Allow current to flow through the wire coil. Sprinkle iron filings onto the acrylic base. Gently tapping the acrylic base will help the iron filings align themselves with the magnetic produced by the coil. Placing the device on an overhead projector will allow the pattern produced by the iron filings to be seen by a large group.
3. Slide the aluminum core into the bottom half of the coil. How does this affect the strength of the magnetic field? Why?
4. Slide the steel core into the bottom half of the coil. How does this affect the strength of the magnetic field? Why?
5. Where is the magnetic field the strongest? Where is it the weakest?
6. Take care when removing the iron filings from the magnetic field viewer as they can scratch the acrylic.