B = UoUrH
The ratio of flux density to field density is not constant but varies with flux density in …show more content…
Let’s say a coil wound on an iron core. A current is applied and flux is produced. When the current is slowly increased and the values of B are plotted against H will us a B – H graph from 1 to 2 like in the diagram above. At point 2 more increase in current would not produce an increase in B and therefore the current is said to be saturated. When the current is turned off at this point, the iron core will stay magnetised and form a permanent magnet.
When the current is slowly reduced from the maximum value and continues to plot B against H, we will get the graph 2 to 3.
In point 3, the current is zero but now that there is a flux because the core is magnetised in a particular direction and it forms a permanent magnet, In order to minimize the magnetic flux to zero, negative current most be applied and this takes the graph to the point