Re: how powerful is the most powerful elecromagnet?

James,

The most powerful magnetic fields created by humans can be found in
the National High Magnetic Field Laboratory located at the Los Alamos
National Laboratory in New Mexico (http://www.lanl.gov/mst/nhmfl)
and at Florida State University in Tallahassee (http://www.magnet.fsu.edu)

The highest continuous magnetic field strength is 45 tesla, achieved
in Tallahassee (http://www.magnet.fsu.edu/news/pressreleases/121799.html)

The highest pulsed magnetic field is achieved by destroying the magnet:
1000 tesla for 4-8 microseconds at Los Alamos and at Sarov, Russia
(http://www.lanl.gov/mst/nhmfl/magnets.html)

For comparison, the Earth's magnetic field has an average value of
0.00005 tesla, and those neodymium-iron-boron magnets ("rare-earth"
magnets) that are almost impossible to separate produce a field of
about one tesla.

The magnetic field (B) of an electromagnet is directly proportional
to the current running through the windings.  It is usually true that
higher voltage implies higher current, but in this case current is
the more fundamental quantity because given the current and the
geometry (solenoid, toroid, or whatever) one could calculate the
magnetic field.  The voltage and the geometry are insufficient to
calculate the magnetic field; one would also need to know that the
winding material is ohmic and its resistance.

--Randall J. Scalise    http://www.phys.psu.edu/~scalise/