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## calculating Gauss of electromagnet

It's been many years since I studied this so I would appreciate some confirmation on the formula and its parts.

The formula I was taught to calculate the Gauss of an electromagnet was: B=MNI/2R
with: B = Magnetic flux in Gauss
M= Magnetic permeability of core material
N = Number of turns of wire
I = Current input in Amps
2R = two times radius (or diameter) of core

Question... is this formula correct?

I have noticed that the term Tesla is favored over Gauss. As I recall, 1 Tesla equals 10,000 Gauss. Am I correct?

I have been quoted by a metal manufacturer that the magnetic permeability of Nickle-Iron is 1,000,000 (one million). That same manufacturer said that NdFeB was 900,000. Do these numbers represent μ? Are these figures proper inputs for the above formula?

So lets create a hypothetical electromagnet. We'll use a .25" diameter by 12" long Nickle-iron rod as the core.

Using 24 Ga magnet wire (.0201") we can wind a coil 12" long by 7" in diameter. This would equal 220,000 turns of wire. If we then supply it with 500 mA of current it should look like this:

B = 1,000,000 x 220,000 x .5 / .25

B= 110,000,000,000 / .25

B = 440,000,000,000 or 440 Billion Gauss

Here's my problem:
The Mag Lab outside Tallahassee Florida claims to have built the world's strongest electromagnet which is 45 Teslas (450,000 Gauss) in strength.

So where have I screwed up in this calculation?
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