Iron core solenoid questions

1. Nov 24, 2015

sa1988

1. The problem statement, all variables and given/known data

Iron core solenoid, with 50 turns per cm (5000 per metre)
Current = 0.2A
Measured B field = 1.58T

Calculate:
i) The applied field, Bapplied
ii) The magnitude of magnetisation, M, of iron alloy

2. Relevant equations

For a long solenoid, Bapplied0nI
And, generally, B=Bapplied0M

3. The attempt at a solution

I'm actually confused mainly on the first part because the answer isn't as it seems.

For a solenoid, the applied field is:
B=μ0nI

So I get B = 1.26E-6 * 5000 * 0.2 = 1.26mT

This would then suggest, for part ii), that the magnetisation for the iron alloy is (1.58 - 0.00126)T = 1.579T

It seems the iron alloy has been rather hugely magnetised by such a small applied field!
I worry if this is actually correct, or I've done something wrong..?

Thanks

2. Nov 24, 2015

TSny

Is this the value for M or for μ0M?

Yes. Ferromagnetic materials are amazing!

3. Nov 25, 2015

sa1988

Ah, oops, yeah I missed out the μ0 term.

Still I was shocked by the seemingly huge resultant B field from such a tiny current in the solenoid.

So M = (B-Bapp)/μ0 = (1.58-0.00126)/μ0

However I'm now shocked again because this gives a magnetisation of 1.25E6... which is huge! (Or is it...?) I can't seem to find any examples online with actual numerical values for me to consider as a reference towards my own answer.

Simply, I don't know what a typical magnetisation value should look like. Should it be as huge as that?

Thanks

4. Nov 25, 2015

TSny

Yes, your numbers look reasonable for iron. It is amazing and it shows what a large group of entities (atoms) can accomplish when they cooperate.

5. Nov 25, 2015

sa1988

Great stuff, thanks