SCIENCE PHOTO LIBRARY SCIENCE PHOTO LIBRARY
Solenoid demonstration. This was a hypothetical observer drawn by Ampere to help illustrate the direction of flow of electric currents and magnetic fields. An electrochemical cell (battery, lower left) powers the circuit, while the iron bar about to be placed in the solenoid (coiled wire) will be magnetised. This illustration is from 'Physique Populaire' (Emile Desbeaux, 1891).
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