# How would be the figure of the magnetic field in a circuit likes this? (image in post)

The circuit consists of a single magnetic material piece (like soft iron) and a solenoid half immersed on it, as in the image below:

I'll feed DC current to the solenoid, and I'm trying to imagine the figure made by the magnetic field lines in the piece and more specifically: if they are going to "cross" the solenoid, producing a force on it.

Could you help me figuring it out?

Thanks!

You see, that in the upper half of the solenoid the magnetic field vector $$\vec{B}$$ has not only a component vertically upwards, but also a component radially outwards. And especially across the gap between the iron pieces there is a strong magnetic field pointing radially outwards. Determining the Lorentz force $$\Delta\vec{F}= I\Delta\vec{\ell}\times\vec{B}$$ acting on a piece of wire $$\Delta\vec{\ell}$$ there, you find that the force $$\Delta\vec{F}$$ has a component downwards. Hence the solenoid is pulled down.