[Physics] Will a hollow ferromagnetic core for a solenoid yield any benefit as opposed to a solid metal core

Question

I'm creating solenoids for a project of mine, wrapping magnet wire around a ferromagnetic piece of pipe by hand. I've heard that the field strength of a solenoid can be increased by an order of magnitude by being wrapped around a solid ferromagnetic core. Since the pipe is obviously hollow, would a ferromagnetic piece of pipe have any benefit to the solenoid wrapped around it?

Answer 1

Yes. The equation and relative permeability is based on solid cores.

The volume for the solid and hollow cores would differ greatly. Specially if you have a high perm material with a hollow air core vs a solid one.

Think of it this way:

Calculate the field for air and iron cores (use online calculator if you have to).

So IronField > AirField right? Cause Iron's relative permeability is higher. Air's permeability is around 1, where as Pure Iron is like 5000.

Now lets say you have a hollow core. From volume calculations and measurements you know that the hollow core is 50% Iron and 50% Air in terms of volume. Now to solve for that hollow core field:

IronField*50% + AirField*50%.

That is less then having a solid core. Hope this helps!