Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Electromagnets: field pattern

Class practical

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

Cardboard

Iron filings

Plotting compass

Power supply, low-voltage ('Westminster pattern' very-low-voltage supplies are best)  

Health & Safety


Warn the class to keep fingers away from eyes. Iron filings inadvertently carried to the eyes can damage the cornea.

Read our standard health & safety guidance

 

Procedure


Electromagnets: field pattern

a 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.

b Wind twenty turns of PVC-covered copper wire round one arm. Connect it to the DC terminals of the low-voltage power supply.
 
c Switch on, and investigate the magnetic field produced. Identify N and S poles.

 

Teaching notes


1 There is no field pattern around the C-cores until a current passes through the coil wrapped round the C-core. 

2 A compass needle will indicate that the two ends of the C-core have opposite magnetic poles.


 
This experiment was safety-checked in July 2007