# Intuition of why total magnetic field decreases with air gap?

Consider two simple magnetic circuits shown below. Both are made of ferromagnetic material but the right one has also an air gap.

If we close the switch $S$ and we wait long enough, the magnetic field $B$ will set up in both circuit. If we use Ampère's law $$\oint \vec{H} \,d\vec{l}$$

we can easily find $B$ and see that it is smaller in the second circuit with air gap.

Question : Without talking about reluctance or making any electric circuits analogy, can someone explain why it is the case? What happens as soon as we close the switch that makes $B$ not able to grow as much in the presence of the air gap?