What happens if an elephant bumps onto a whale?

“From two to five” by K. I. Chukovsky

This is the question (or a similar one) that arose in my mind after remembering an experiment I had seen.

A physics teacher showed a group of 35 people, including me, the following experience:

A horizontal copper disk on an axis, rotated by a handle through an accelerating “gearbox”.

Above the disc, at a distance of 1-2 cm, there is a rather thick glass sheet that completely overlaps the dimensions of the disc. There is a needle with a magnetic needle from the compass exactly above the axis of the disk.

The teacher started spinning the copper disc and, o miracle, the magnetic needle also started spinning in the same direction as the NON-MAGNETIC copper disc.

Then the teacher suggested that we all try to explain this strange phenomenon. which is called the “Arago Experiment”, in honor of the famous French physicist and astronomer D.F. Arago, who invented this experiment at 1824.

During the break between the two parts of the seminar, I approached the teacher and timidly asked if I could tell him about the reasons for this behavior of the magnetic needle.

(By the way, as it turned out later, I was the only one from the group of listeners who tried to give an explanation).

The teacher agreed with some surprise, but readily (I was NOT listed in the “table of ranks” of particularly capable and, in general, capable).

The explanation is simple: The magnetic needle creates its own magnetic field, which, due to the rotation of the copper disk, generates Foucault induction eddy currents in it, directed according to Lenz’s Rule so that its fields REDUCE the CHANGES in the magnetic field that caused them! This means that due to the interaction of two such magnetic fields, the disk pulls the arrow along with it precisely because then the total change in its field relative to the copper of the disk will be minimal, reduced, which is what Lenz’s Rule says.

The teacher completely agreed with my explanation and included me in his thoughts among the most capable listeners.

And why didn’t others, much more capable and successful, GIVE an explanation, even though the teacher suggested this task to EVERYONE?

Am I the only one who’s become such a “genius” explainer?

No!

I just have a childish “why” in me. PERSONALLY, I wanted to explain convincingly for myself what “secret” mechanisms and forces caused the arrow to spin, separated from the non-magnetic disk by a piece of glass.

And others, capable and talented, who easily cope with difficult scholar exercises to questions for which there will be NO excellent marks are given in the relevant official documents (for further proud presentation!) were deeply indifferent. I’m sure they would have solved this problem not worse, but better than me, but they were NOT INTERESTED, INQUISITIVE, and NOT purely childish, like me.

That’s the difference!

It was just an introduction.

And now let’s move on to another mental experience.

Let’s imagine a kind of ribbon made of a dielectric (insulator), which is moving with any chosen velosity by a motor remote from the “work area”. Electric charges are rigidly and evenly fixed on the tape, no matter what polarity. So, there is a certain part of the tape that is shielded from all external electric and magnetic fields. This is what I called the “work area or section”. We will fix the magnetometer at some small distance above the tape. If the tape is at rest relative to it, there is no magnetic field. But with any movement, there is an “electric current” – a directed and orderly movement of charges, causing the appearance of a magnetic field at the point of the magnetometer. The higher the speed of the tape (at a constant charge distribution density on it), the greater the magnetic field created by them. (Slightly modified Rowland’s experience)

We will place a copper strip at about the same distance as the magnetometer, the plane of which is parallel to the plane of the “working section” of the dielectric tape and equal in length to it.

How will our “work section” affect it?

If it is stationary, then its resting electric charge will induce some charge displacement in the copper strip and create a small transverse polarization.

If the working tape is moving, it will continue to create electrostatic polarization across the plane of the copper tape and a magnetic field penetrating the copper without any effects.

But here a certain “little trick” is revealed. According to the concepts of the part of theoretical physics, called “Electrodynamics”, the electric field of a point charge at rest has a spherical shape, its equipotential surfaces (surfaces of equal, same potential) are spheres. But for a MOVING charge, the vectors of its “lines of force” turn slightly forward, depending on the magnitude of the velocity. That is, its field has now a certain component directed not strictly radially (radius vector) from the center of the charge, but slightly forward, parallel to its velocity vector in the ratio v/c, where v is the velocity of the charge and c is the speed of light. In our case, this means that this “velocity component” must somehow affect the electrons in the copper strip and drive them in the same direction as the moving “working tape”. This means that if you connect a sensitive potential difference meter to the ends of the copper tape (like the “mirror galvanometer” used for many years), it should register a certain low voltage between the ends of the copper tape.

It can be argued that the magnetic field, which is constant for a magnetometer, is not constant for copper electrons and it moves, dragging electrons with Foucault currents, induction currents.(let’s just recall the described experience of Arago!)

Then we will improve our experiment – we will try to eliminate the possible influence of the magnetic field of the “work tape”.

We will apply a thin copper strip to the dielectric tape, but with neatly made holes of such a diameter that they only surround the charges, but do not come into contact with them in any way, that is, the charges remain isolated from each other on the dielectric and are not connected by a perforated copper plate.

And then we will start passing a current through the pad that is exactly equal in magnitude to the “current” created by the movement of the tape, but creates a magnetic field that is opposite to the field of movement of the “working tape”, that is, almost completely compensating for it.

If the galvanometer will still show a certain potential difference, then it is created by the longitudinal component of the electric field of the moving charge.

If there is no voltage when the “compensation current” is turned on, then its initial detection is due not to the electrostatic field, but to the magnetic field of moving individual charges.

In general, we combined two experiences: Rowland and Arago, and added another element -a sensor – a copper tape.

To summarize: An experiment is proposed that proves or refutes the theoretical idea of the rotation of radius-vector of a moving electric charge in the direction of its movement.

Visually, it would look like turning a sphere into an ellipsoid with a ratio of long and short according to the formulas of Special Relativity, the longitudinal axis is slightly lengthened and the transverse axis is slightly shortened, with the charge being in its “rear” focus.

Literature:

L.D. Landau, E.M.Lifshits, “Field Theory”

V.Panowski, M.Phillips, “Classical electrodynamics.”

M.A.Tunnela, “Fundamentals of electromagnetism and the Theory of Relativity”

R.V. Paul, “The Doctrine of electricity”

9 VII 2026

P.S. Answering readers’ asked and/or silent questions about the reasons for my publications on portals generally intended for writers, I would like to inform that NO “SCIENTIFIC JOURNAL” will ever publish my notes (my stupid attempts to do this brilliantly confirmed what I have just said!) and therefore, I consider it possible to invite any readers with any special education to familiarize themselves with my thoughts and topics, regardless of their agreement with them or their total rejection, to contribute to the process called THINKING.