When teaching electromagnetism in schools, many teachers make use of an apparatus similar to this:


Image source.

This got me wondering, does the mass of the iron nail affect the strength of the magnet?

  • $\begingroup$ How would you change the mass of the iron, exactly? Making it longer (more turns)? Making it thicker (more area)? Making it denser (different element that's not ferromagnetic)? $\endgroup$
    – endolith
    Aug 8 '16 at 21:00

I believe this scenario would be mass independent. The strength of a solenoid's field with no core is B=unI while the strength of a solenoid with a core is B=kunI with k being a constant which is the relative permeability of the core substance. As you can see, by just adding a constant with a core, it would be mass independent.

B = Magnetic field strength (Teslas)

u = Permeability of free space (1.26*10^-6 Tm/A... I actually don't remember the rest of this unit)

n = The number of turns over the length of the wire. You will also see this written as N/L.

I = The current flowing through the wire (Amperes)

k = The relative permeability of the core substance (dimensionless)


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