How much electromagnetism does one need to lift 10 pounds?

Question

I am new to electromagentism and am wondering how much voltage would be required to secure an electromagent to a ten pound iron/steel weight.

Answer 1

Well, to start with, it's current that's directly linked to the strength of an electromagnet, not voltage.  For a coil of N turns that's L meters long, the field generated along the axis is approximately:

B = (μ0)Ni/L

Where μ0 is a constant and i is the current.  In practical terms, if you have an iron core for the coil, the field at one end will be about equal to the value above.  If you have an air core, it'll be about half the value above.

Turning that into a force on metal, however, is more advanced work.  As in, I dimly recall doing it in grad school, but I can't remember how to do it anymore.  It involves the divergence of the magnetic field, I think, which means the equation I provided above is WAY too simplified to be useful, since you'd need the full gory details to perform the differential operation.

However, it does scale more or less linearly with current, and for a given electromagnet the current will be directly related to the voltage.  So if you find that 10V will lift 1 lb for your magnet, then you need 100V to lift 10 lbs.