Electromagnets: field pattern
Practical Activity for 14-16
Exploring the magnetic field pattern for a C-core.
Apparatus and Materials
For each student group
- Copper wire, PVC-covered, 150 cm with bare ends
- C-core, laminated iron
- Plotting compass
Health & Safety and Technical Notes
Warn the class to keep fingers away from eyes. Iron filings inadvertently carried to the eyes can damage the cornea.
- Take an iron C-core, place a card on top, and sprinkle with iron filings. Is there any magnetic field pattern? Test with a plotting compass.
- Wind twenty turns of PVC-covered copper wire round one arm. Connect it to the DC terminals of the low-voltage power supply.
- Switch on, and investigate the magnetic field produced. Identify N and S poles.
- There is no field pattern around the C-cores until a current passes through the coil wrapped round the C-core.
- A compass needle will indicate that the two ends of the C-core have opposite magnetic poles.
This experiment was safety-tested in July 2007