Faraday's 1831 induction experiments: reported transients and the iron-ring apparatus

Primary source and reading limits. Michael Faraday, Experimental Researches in Electricity, Volume I, First Series (read 24 November 1831), 1849 collected second edition, read in the Project Gutenberg transcription derived from BnF/Gallica images; the First Series paragraphs 1-33 were read completely, and no claim is made to have read the whole volume. This is an original report reprint transmitted by a later transcription, not a newly repeated experiment. The account below is the report's apparatus descriptions and reported observations, structured by the record contract of Report-backed operational evidence with uncertainty; it is not a deduction, and 'no perceived deflection' is everywhere the report's finite-resolution verbal observation.

Insulated copper helices wound on a wooden cylinder, each containing about twenty-seven feet of wire and kept from touching by interposed twine, twelve helices superposed in the same direction with the first, third, fifth, seventh, ninth and eleventh joined into one helix and the remainder into a second (paragraph 6). A pair of two-hundred-and-three-foot coils interleaved as a spiral on a wooden block with metallic contact prevented by twine (paragraph 10). A small hollow helix wound on a glass tube into which a steel needle could be inserted (paragraph 13). Insulated zigzag wire boards moved relatively to one another (paragraph 18). A welded soft-iron ring, seven-eighths of an inch thick and six inches in external diameter, with three insulated inducing helices A of about twenty-four feet each and a separate helix B made from about sixty feet of wire in two pieces. The A helices were joined end to end and connected to a battery of ten pairs of plates; B was connected to a galvanometer three feet from the ring (paragraphs 27-28). Paragraph 31 reports the ring trial with one hundred pairs; paragraph 11 reports a separate coil trial with one hundred and twenty pairs.

Making and breaking the battery circuit of the inducing helix while the detector loop is kept complete (paragraphs 10-11); removing the inserted needle before breaking the battery contact, and inserting it after make but before break (paragraphs 13-14); completing the detector circuit before the battery contact is made or broken (paragraph 17); moving the zigzag boards together and apart with a steady battery current (paragraphs 18-19); reversing the direction of the battery connection (paragraph 30); repeating with larger batteries and with charcoal contacts (paragraphs 31-32).

A slight deflection of the galvanometer needle at the moment of completing the connection, always in one direction, with the opposite deflection at breaking, and no sustained perceived deflection under the continued steady battery connection (paragraphs 11 and 28-31); magnetization of an inserted steel needle, with opposite poles at make and at break and near-cancellation when both transients act on the same inserted needle (paragraphs 13-17); opposite transient deflections as the boards approach and recede, with return to the ordinary position when the movement ceases (paragraphs 18-20); a minute spark at the secondary helix with charcoal contacts (paragraph 32); and the control that, after the first effect, the galvanometer needle resumes its position under the continued battery current (paragraphs 28 and 33). These are reported finite-resolution qualitative observations.

The read passages identify deflection direction, needle-pole comparison, battery reversal and background and timing controls, but supply no calibrated conversion from deflection to current, no detector response or transfer function, no trial-level dataset, no declared sampling law, no error bars and no formal significance test; dimensions, wire lengths and battery plate counts are historical approximate apparatus descriptions, not modern precision estimates. The sign interpretation of the induced current depends on galvanometer and needle response conventions. Missing information is retained as missing; no error bars, precision or independence are invented.

The reported observations support a transient induction model for the described apparatus under the stated apparatus assumptions and are qualitatively consistent with conditional framework predictions of transient induction where those are instantiated for the described circuits; they do not establish a universal exact induction law, do not isolate all auxiliary assumptions (magnetic inertia, switching transients, leakage, current history, geometry) and supply no quantitative model comparison. The empirical support is a nonlogical relation to the induction predictions, not a proof of any postulate, and the source limitations of the reading travel into any downstream conclusion.