How will the force between the two poles change if the two poles are connected by an iron rod keeping the distance between two magnetic poles constant?
A. Increases
B. Decreases
C. Remains same
D. None of these

Hint:The concept of magnetic flux tells us that the ability of the magnetic material to allow the magnetic field lines to pass through it. We will be using this concept to decide whether the value of magnetic flux will increase on the introduction of the iron rod between two magnetic poles.

Complete step by step answer:
It is given that the magnetic poles are connected by an iron rod keeping the distance between them constant, and we have to find out the effect of the introduction of iron rod on the force between two poles of a magnet.
We can easily understand that when there was no iron rod between the poles of the given magnet, the air was acting as a magnetic medium. After the introduction of the iron rod between the magnetic poles, the magnetic medium is shifted to the iron rod from air. We know that the magnetic flux of the iron rod is very high as compared to the magnetic flux of air. In other words, we can say that the permeability of magnetic force in iron is less than that of air.
We also know that iron rod is a ferromagnetic material which means if it is placed in a magnetic field for a sufficient amount of time its molecules will permanently align in the direction of the magnetic field of a magnet to which it is subjected, resulting in conversion to the permanent magnet.
Therefore, based on the above explanation, we can say that the force between the poles of a magnet will increase due to the introduction of the iron rod between the poles and the option (A) is correct.

Note:Permeability of a magnetic material means the ability of the magnetic material to resist the magnetic field lines to pass through it. If the magnetic field allowed to pass is very much then the material is termed as less permeable magnetic material.