In addition to increasing the coil number of turns, we also can by means of increasing the length of the coil diameter or the core to increase inductance.
In both cases, need more line to coil structure, there are many lines of force to produce the required counter electromotive force.
If the coil winding on the iron core, namely the iron core is made of soft iron material, the winding on the ferromagnetic or hollow tubular coil inductance can be further increased.
If the inner core, such as soft iron, cobalt and nickel some of the ferromagnetic material, the coil inductance will increase greatly, because for the same amount of current, the magnetic flux will be strong.
This is because we see in the tutorial, material through the soft iron core material strongly focused line of force.
So, for example, if the core winding core materials have relative permeability is greater than the free space.
Soft iron or steel, for example, the coil inductance, so we can say that the inductance of the coil is proportional to the increase with the increase.
And then used to revolve around before or at the top of the core will need winding coil inductance equation and stated to be modified to include the relative magnetic permeability of materials.
If the coil winding on the iron core, will lead to large inductance, because the magnetic core's permeability will change with the magnetic flux density.
Depends on the type of ferromagnetic materials, however, the inner core flux can reach saturation, resulting in a nonlinear inductance value.
Due to coil around the magnetic flux density depends on the flow through the current, so the inductance has become the current function, the electric current.
In the next tutorial of inductor, we will see the coil magnetic field is produced to make electric current flows through the placed next to the coil.
This effect is called mutual inductance, the transformer, the basic working principle of electric motors and generators.