Length Of An Opti Boat How Does The Size And Length Of The Core Affect The Magnetisation Of An Electromagnet?

How does the size and length of the core affect the magnetisation of an electromagnet? - length of an opti boat

In particular, I am tempted to an electromagnet with a magnetic coil, which build only less than half the distance from the plant to ensure that the core extends from the end of the coil. Magnetize By activating the electromagnet to the whole kernel, or only partially covered by the coil? Also, as the core diameter and length of the base outside of the magnet affects the overall intensity of magnetism? And apart from soft iron (which is impossible to obtain in those days, believe it or not), there are very good materials that can be used for the base? Stahl was a suggestion. Thank you!