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Magnetisation of a plain fluid, two ways

The same calculation run twice, side by side. Change anything on either side and the difference is shown output by output. This page is a link: both sets of numbers are in the address bar.

Side A open alone

The plain fluid or gas in the tube, with no particulate. Its own volume susceptibility is the whole answer.

kA/m

The drive coil's field in the tube. 50 kA/m is about 63 mT in air — a strong solenoid.

bar

For a gas, the density and with it the susceptibility scale with pressure; a liquid ignores this.

Side B open alone

The plain fluid or gas in the tube, with no particulate. Its own volume susceptibility is the whole answer.

kA/m

The drive coil's field in the tube. 50 kA/m is about 63 mT in air — a strong solenoid.

bar

For a gas, the density and with it the susceptibility scale with pressure; a liquid ignores this.

Swap sides

What changed

The two sides are the same. Change something on either.

Output A B B against A
M Magnetisation -0.452 A/m -0.452 A/m same
χ Susceptibility -9.04e-6 -9.04e-6 same
ΔB Added flux density -568 nT -568 nT same

Side A, with its numbers

-0.452 A/m=-9.04e-6⁢50 kA/m,-568 nT=μ0⁢-0.452 A/m
LaTeX 
-0.452\,\mathrm{A/m} = -9.04e-6 \cdot 50\,\mathrm{kA/m}, \qquad -568\,\mathrm{nT} = \mu_0 \cdot -0.452\,\mathrm{A/m}
  • Water is diamagnetic: its susceptibility is 9.04 parts per million and negative, so in the coil's field it magnetises against the field and is pushed very slightly out of it rather than drawn in. The magnetisation is -0.452 A/m, and a 5 % slurry of micron iron in this field carries about 16,600 times as much, the other way.
  • No remanence exists in a plain fluid or gas. A diamagnet or paramagnet is magnetised only while the field is on it; the instant the medium leaves the drive coil it is unmagnetised, and nothing is carried to a downstream coil. What a pickup coil would see from this medium is the drive coil's own field through the medium's parts-per-million, not anything the medium brought with it.

Side B, with its numbers

-0.452 A/m=-9.04e-6⁢50 kA/m,-568 nT=μ0⁢-0.452 A/m
LaTeX 
-0.452\,\mathrm{A/m} = -9.04e-6 \cdot 50\,\mathrm{kA/m}, \qquad -568\,\mathrm{nT} = \mu_0 \cdot -0.452\,\mathrm{A/m}
  • Water is diamagnetic: its susceptibility is 9.04 parts per million and negative, so in the coil's field it magnetises against the field and is pushed very slightly out of it rather than drawn in. The magnetisation is -0.452 A/m, and a 5 % slurry of micron iron in this field carries about 16,600 times as much, the other way.
  • No remanence exists in a plain fluid or gas. A diamagnet or paramagnet is magnetised only while the field is on it; the instant the medium leaves the drive coil it is unmagnetised, and nothing is carried to a downstream coil. What a pickup coil would see from this medium is the drive coil's own field through the medium's parts-per-million, not anything the medium brought with it.