one characteristic of magnetic lines of force is that they repel each other, never crossing and uniting. if two magnetic fields are placed near each other, as illustrated by the placement of the two magnets, below, the magnetic field will not combine but will distract a flux pattern(Not that the flux line does not cross each other.)

 There are no known insulators for the magnetic lines.it has been found that flux lines will pass through all materials. however, they will go through some materials more easily than others. this fact makes it possible to concentrate flux lines where they are used or to bypass them around an area or instrument.     

On the previous sheet, you were told that the magnetic line of force will go through some materials more easily than through others. these materials which will not pass flux lines so readily, or which seem to hinder the passage on the lines, are said to have a comparatively high reluctance to the magnetic field of force. reluctance, reference with a magnetic circuit, is roughly the equipment of resistance when an electric circuit will consider.   

Magnetic lines of force take the path of least reluctance; for example, they travel more easily through iron than through the air. since air has a greater reluctance than iron, the concentration of the magnetic field becomes greater in the irons (as compared to air ) because the reluctance is decreased .in other words addition of iron to a magnetic circuit concentrates the magnetic field which is in use.

Magnetic lines of forces act like stretched rubber bands. the figure below suggests why this characteristic exists, particularly near the air gap . not that some line of force curves outward across the air gap in moving from the north pole to the south poles. this outward curve, or stretching effect, is caused by the repulsion of each other magnetic lines from its neighbor. however, the line of force tends to resist the stretching effect and therefore resembles a rubber band under tension.

AS has already been mentioned,  magnetic lines of forces tend to repel each other. by teaching the flux pattern of the two magnets with like the pole to gethers, in the diagram below, it can be seen why this characteristic exists.

The reaction between the field of the two magnets is caused by the fact the line of force cannot cross each other. the lines, therefore, turn aside and travel in the same direction between the pole force of the two magnets since lines of the force which are in such manner tend to push each other parts,the magnet mutually repels each other.