Strength of magnetic field on "eBay electromagnets"?

[Sven Andersson]

How strong, approximately, is the magnetic field, on a powerful electromagnet, that you buy on eBay, that can lift, say, a 100 kg?

 

[Dr. Courtney]

Hard to say. It is uncommon for permanent magnets to exceed a couple Tesla. Force is increased by increasing the area over which the magnetic field is applied, not by increasing the magnetic field itself, due to material limitations.

For big magnets, lifting force or total dipole moment is a more reasonable metric than field strength at the surface.

 

[davenn]

It is uncommon for permanent magnets to exceed a couple Tesla. Force

he's referring to electromagnets

How strong, approximately, is the magnetic field, on a powerful electromagnet, that you buy on eBay, that can lift, say, a 100 kg?

Sven, your Q is very vague ... how about a link to the eBay electromagnets in question

and whilst doing that, have a look at the wiki entry on electromagnets ...
https://en.wikipedia.org/wiki/Electromagnet

Dave