reluctance
resistance
reactance
conductance
increasing and decreasing the number of turns of the coil
using an exciting coil with number of tappings
varying the current through the exciting coil
varying the core position of the exciting coil
Helix rule
End rule
Right hand grip rule
Fleming's right hand rule
1
2
3
4
Out of the east pole into the west pole
Out of the west pole into the east pole
Out of the north pole into the south pole
Out of the south pole into the north pole