A. This question has two parts. The first part involves amperes law concerning the strength of an electromagnet as measured in Tesla. Amperes law states that the strength of the B field of the strength of the electromagnet is determined by ampere turns and current in said turns known as MMF.

Yet amperes law is based on the permeability of the wire used for said ampere turns of one. What if we used a permeability of 1000 times that (iron). Wouldn't the magnetic field of the current be amplified for each turn of an electromagnet if a high permeability wire were used instead? Would that not increase the strength of the electromagnet by thousand fold?

B. If an electromagnet has a core made up of ten individual iron wires, each insulated from the other, but part of the same magnetic circuit with parallel reluctance, wouldn't each wire magnetize, and seeing how magnetic fields are cumulative, would this not create a stronger total Flux than one core of equal cross area? If a single core of same cross area had 0.1 Tesla but with the core with ten iron wires and each magnetic field is cumulative, it's total field strength would be 0.1 Tesla x10? The core with 10 wires all have the same 90 degree winding around all ten so to each wire it appears the same ampere turns or MMF.

  • \$\begingroup\$ The electromagnet I refer to in both instances is a closed loop and has no air gap. Iron is a poor conductor but it's permeability is a thousand times that of copper to amplify the magnetic field of the current. So required length should be a thousand times less, than for copper. \$\endgroup\$
    – Bruce-TPU
    Nov 17 '16 at 12:39
  • \$\begingroup\$ Include a detailed diagram. Andy is right about electromagnets and I frankly don't know what you mean about one that has no air gap. While the magnetic force surfaces terminate on the current that generates them, and this requires the magnetic force (which is one part of the magnetic field) to penetrate a wire to reach those charges, permeability is about flux density, which is the other part of the magnetic field. The highest flux density is inside the coil and perpendicular to the circular loops of wire. The whole idea seems misguided. But perhaps a diagram will clear that up. \$\endgroup\$
    – jonk
    Nov 17 '16 at 19:12
  • \$\begingroup\$ An electromagnet core is a magnetic component. The electromagnet's windings are NOT a magnetic component, and their magnetic permeability is not important. \$\endgroup\$
    – Whit3rd
    Dec 18 '16 at 7:19

Iron is a poor conductor compared to copper so making an electromagnet from iron wire is off to a bad start. Next, an electromagnet has basically a massive air gap and this is the bit that attracts i.e. the working end of an electromagnet is the air gap. This is generally why the attractive force produced by a solenoid electromagnet has nothing to do with the permeability of the core: -

Force = \$(N\cdot I)^2\cdot 4\pi 10^{-7}\cdot \dfrac{A}{2g^2}\$

  • F = Force
  • I = Current
  • N = Number of turns
  • g = Length of the gap between the solenoid and the magnetizable metal
  • A = Area

Would that not increase the strength of the electromagnet by thousand fold?

Yes or No if it saturates the magnetic flux capacity, then it behaves like resistor wire and drawn much more current.

You seem to understand the relationship of variables that affect Magnetic field in Tesla units but are not familiar with the properties of materials.

Air does not saturate or have hysteresis while magnetic materials with high mu do saturate and have a wide range in properties.

Generally Ferrite limits range from 0.5 to 0.7T in the best materials, while the best Cold Rolled Grain Oriented Steel (CRGOS) laminations (used in large transformers) start at 5 ~ 7 Tesla and may exceed 10T with exotic expensive materials. Lamination loss ,issues measured in Watts/kg decrease with thickness and require a silicate insulative coating.

Magnetic ferrite has nano particle non-magnetic gaps in the material while steel uses silicate gaps and special airgapped transformers can store more energy using the calibrated air gap.


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