Soft Iron for an electromagnet
Soft Iron for an electromagnet
(OP)
Hey, I read somewhere that soft iron was the best to use in the core of an electromagnet.
I found this disk-shaped piece of what seems like iron in the base of an old lamp. Its got a dark-silver metallic color, it's magnetic, and has a density of very roughly 8370 kg/m3(volume was measured by geometry, not liquid displacement).
How can I tell what kind of iron, if it is iron, this piece of metal is?
I found this disk-shaped piece of what seems like iron in the base of an old lamp. Its got a dark-silver metallic color, it's magnetic, and has a density of very roughly 8370 kg/m3(volume was measured by geometry, not liquid displacement).
How can I tell what kind of iron, if it is iron, this piece of metal is?





RE: Soft Iron for an electromagnet
A direct current electromagnet would still need to use a laminated core. Otherwise, eddy current would prolong buildup and decay of the magnetic field when energized and deenergized respectively.
RE: Soft Iron for an electromagnet
RE: Soft Iron for an electromagnet
RE: Soft Iron for an electromagnet
RE: Soft Iron for an electromagnet
RE: Soft Iron for an electromagnet
From the previous discussion I understand that you have no basic knowledge of magnetic circuit theory. To create a strong magnet you have to design the magnet such that the coil in encapsulated inside an all around iron body this way all the magnetic flux will flow in the iron parts with very limited leakage to the air. The piece of steel that you are planing to pull will be the closing part of the magnetic flux circuit.
If it is a private home project I suggest that you should do some reading on the sujbect. The best is the book Electromagnetic Devices by Roters 1941 which is quite rare but you may find it in the nearby university library.
If it is a work project I would recommend hiring an expert consultant.
RE: Soft Iron for an electromagnet
http://www.arnoldmagnetics.com/mtc/manuals.htm
If you want a simple electrical analogy:
flux Φ ≡ current I
mmf F ≡ voltage V
reluctance S ≡ resistance R
- so from ohms law:
Φ = F/S
also Φ = BA (flux density x cross sectional area)
mmf F = NI (number of turns x current)
S = l/μA
where l=length of magnetic path and μ=permeability
- analogous to the equation for electrical resistivity
R=l/σA
i.e. permeability ≡ electrical conductance, the reciprocal of electrical resistivity.
All the above is in SI units.
The magnetic circuit (as referred to by israelkk above) can be considered analogous to a series electrical circuit with either a magnet or a coil representing the voltage source and resistors representing the iron and air parts.
The problem you have is that for a large pole piece i.e. large A, you also need a lot of magnetizing force F (i.e. a large coil with plenty of current) to get a high flux density B.