In this paper, we utilize the readily known theory of the ideal transformer to furnish a self-contained qualitative explanation on the AC-powered Thomson jumping ring (TJR) experiment.

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The two voltages in Eq. (1) are PDs, or both are EMFs. The requirement “power input to the primary coil = power output from the secondary coil” corresponds to “PDpri×Ipri = EMFsec × Isec.” As EMF = –PD,5 the most correct current ratio is negative. Ignoring the negative sign does not affect our qualitative reasoning.
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The input side transforms the input electrical energy to magnetic energy and stores it in the core. At the same moment of its creation, all this magnetic energy is taken by the output side and transforms to the output electrical energy. The output takes away all this magnetic energy; no residue of the corresponding magnetic flux (energy) is left over.
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13.
Assuming Iring=I^ringcos(ωt) in Eq. (7), we will get Itotpri=I^totpricos(ωt+θ), where θ = π/2 + tan−1(Lring/R). Instead, we can assume Itotpri=I^totpricos(ωt), and then find Iring=I^ringcos(ωt+θ). The former is the transformer (with M) method, while the latter is the standard RL method.
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