The interesting case of mechanical induction modulation.

[broli]

Yes the flux is constant I know. It's like when you have a powered air core and would quickly introduce a core into it. Since the flux remains constant the current needs to drop so an induced EMF is generated across the coil which reduces the current momentarily until the core is fully inserted and the battery pushes it back up. Don't you agree?

[broli]

I have been playing around with a air only toroid. I'm still trying to push it as much as possible but currently the outside magnet is able to have a flux linkage on the air toroid that is equivalent to 100 turns at around 1.35A. Which is quite significant.

Edit: What's more bizarre is when powering on the coil as to simulate the resulting forces, the force on the magnets seem to increase as the flux increases, meaning the coil seems like it's aiding the magnet to increase the very flux it's trying to oppose.

Edit2: Looks like the flux linkage is negative implying that it's coming from the flux of the opposite leg of the toroid which makes me think that the flux linkage is just a simulation anomaly. But it's still quite significant.

[F6FLT]

Yes the flux is constant I know. It's like when you have a powered air core and would quickly introduce a core into it. Since the flux remains constant the current needs to drop so an induced EMF is generated across the coil which reduces the current momentarily until the core is fully inserted and the battery pushes it back up. Don't you agree?

Yes, this is the principle. Applied here, it implies this constancy of the current.

The opposition to the flux variation tends to keep constant d(L.i)/dt. The variation of the current should therefore be inversely proportional to the variation of L. And vice versa, because we are not in a causal system. Here L and i are linked, i has as much action on L as L has on i because the field B modifies L according to the saturation curve of the core, and B depends not only on the magnet, but also on i. The two phenomena of change of i and L are concomitant, simultaneous, opposite, and consequently L and i remain constant.

[broli]

Yes, this is the principle. Applied here, it implies this constancy of the current.

The opposition to the flux variation tends to keep constant d(L.i)/dt. The variation of the current should therefore be inversely proportional to the variation of L. And vice versa, because we are not in a causal system. Here L and i are linked, i has as much action on L as L has on i because the field B modifies L according to the saturation curve of the core, and B depends not only on the magnet, but also on i. The two phenomena of change of i and L are concomitant, simultaneous, opposite, and consequently L and i remain constant.

I understand what you mean now and you're right. The change in current is instantaneous which is actually amazing if you think about it. It reminds me of gyroscopic precession where the precession is starts and stops instantaneous as soon as you add/remove the force.

When you pull a core out from a powered solenoid, L goes down too and I rises proportionally and instantaneously seemingly keeping d(L.i)/dt = 0. But do we not see an EMF generated?

[F6FLT]

...The change in current is instantaneous which is actually amazing if you think about it.

It reminds me of gyroscopic precession where the precession is starts and stops instantaneous as soon as you add/remove the force.

I was able to answer quickly because I had seen this in a past experiment on core saturation, where I was very surprised. I agree that it is quite amazing.
It is possible that there is a similar effect with precession, because an electron spin behaves like a perfect magnetic dipole and therefore like a superconducting loop.

When you pull a core out from a powered solenoid, L goes down too and I rises proportionally and instantaneously seemingly keeping d(L.i)/dt = 0. But do we not see an EMF generated?

If the flux variation is cancelled, there can be no EMF. The phenomenon is not contradictory with the classical theory but still seems quite crazy.
I wonder if the proximity of this effect, the total cancellation of the flux variation, to the magnetic flux repulsion effect that we have with superconductors could not be a lead in itself to explore.