2024-09-17
Free oscillations in a non-inductive coil
In general, this experiment is a continuation of the experiments with an inductance coil, where such a phenomenon was first discovered.
But, unlike it, here we tried to isolate the first, most important, in our opinion, oscillation in a series of damped oscillations.
The essence of the experiment is as follows: a non-inductive coil is excited by a short pulse, after which a series of oscillations arise in it, the amplitude of which is unevenly distributed along its length.
The first oscillation is almost independent of the location on the coil, while the amplitude of the damped oscillations depends on the location of the measuring probe.
Watch the next video.
Video 1. Distribution of oscillations along the length of a non-inductive coil
The video shows the coil being studied and the oscilloscope probe, which the experimenter moves along it.
The oscilloscope, however, shows the readings of the electric field around the coil.
Moreover, at the top of the coil, classic damped oscillations are clearly visible, and at the bottom, a single pulse.
The generator is connected from below, and the two windings of the coil are closed at the top, forming two counter-connected inductive circuits.
In addition to the fact that the main (first) oscillation is the same anywhere on the coil, it has a number of other properties.
1) The first oscillation is unipolar.
If you move the oscilloscope probe to the upper end of the coil, then the damped oscillations located at the top are simply added to the main oscillation.
2) The first oscillation does not depend on the ferromagnetic parameters of the coil.
When a ferromagnetic core is introduced, the amplitude and duration of the main oscillation do not change.
But the frequency of the damped oscillations changes depending on the core introduced into the coil, as expected according to the classics.
Next, let's consider the experimental scheme in more detail.
For it, we will select the next generator on a bipolar transistor, which is designated as GG1 in the following scheme (Fig. 1).
Coil L1 is wound on any frame, 40 mm in diameter (or more), with a double wire, the two ends of which are then connected together.
In total, you should get a coil that has no inductance.
Of course, it will not be possible to make such a design ideally, but it will be enough if its winding contains 50 or more turns, and you can wind it in two layers (as the author did).
The diameter of the wire is not particularly important, but to reduce losses due to resistance, and thus slightly improve the effect, wind it with a thicker conductor.
The position of the coil L1 in the diagram is the same as in Video 1.
Fig. 1. Schematic diagram of the experiment with a non-inductive coil
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In this connection, damped oscillations will be observed at the top of the coil L1 (according to the diagram), and the main oscillation will be observed at the bottom.
If the coil L1.1 and L1.2 are connected in series, then inductance will appear in it, the oscillation distribution will become classical, and the effect itself will disappear.
The duration of the first pulse should be 100 ns or less.
The previously proposed generator fulfills this condition.
If we use a generator with a key, for example such,
then for non-inductive coils it will produce pulses longer than 200 ns, which is not suitable for our experiment.
Although even with such a generator the effect will be observed, but very blurred, and the position of the main pulse, when it is clearly observed, can shift beyond the beginning of the coil (bottom of the diagram).
Transmitting properties of a non-inductive coil
If you wind a receiving coil L2 and connect a LED D1 to it, you can see that the glow level of D1 does not depend on the angle of the relative position of L2 relative to the transmitting L1.
This property is mathematically formalized here, and in this experiment it is shown in practice (Fig. 2).
L2 can be wound on the same frame as L1, and contain 30-80 turns of wire with any diameter suitable for you.
Fig. 2. A non-inductive coil emits two magnetic fields
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If you use a super bright LED, then with a voltage of 14 volts on GG1, you can achieve the glow of D1 at a distance of 100-150 mm, regardless of the angle of mutual arrangement of L2 relative to L1.
This tells us about the radiation from the coil L1 as the first (classicalwhom), and the second magnetic field.