A Study of the Joule and Wiedemann Magnetostrictive Effects in Steel Tubes

S. R. Williams
1911 Physical Review  
TN 1842 Joule 1 discovered that an iron rod changed its length •*• when subjected to a magnetic field whose direction was parallel to the axis of the rod. This variation in length with change in magnetic field strength was found to be an increment up to a certain value of the magnetic field beyond which the rod appeared to contract. Later investigators 2 showed that if sufficiently strong magnetic fields were used the bar actually became shorter than when in its virgin state. Some years before
more » ... Some years before this interesting discovery of Joule, Wiedemann 3 found that "if a vertical wire is magnetized with its south end uppermost, and if a current is then passed downwards through the wire, the lower end of the wire, if free, twists in the direction of the hands of a watch as seen from above, or in other words, the wire becomes twisted like a right-handed screw if the relation between the longitudinal current and the magnetizing current is right-handed* "In this case the magnetization due to the action of the current on the previously existing magnetization is in the direction of a right-handed screw around the wire. Hence the twisting would indicate that when the iron is magnetized it expands in the direction of magnetization and contracts in directions at right angles to the magnetization. This agrees with Joule's results." Thus Maxwell 4 explains the phenomenon in his second edition of Electricity and Magnetism and I have quoted directly because in the first edition it is stated oppositely and some of our recent 5 writers have persisted 1
doi:10.1103/physrevseriesi.32.281 fatcat:lq66mnxbbbfmnc33ys3vrs6g2u