Small Magnet: a Steel Bar Magnetised by Electric Induction (Work, 1892)

A permanent magnet made from a steel bar. Work (1892) names three ways to magnetise steel: single touch, double touch, and electric induction. Induction needs no magnet to start with: wind several coils of insulated copper wire over the bar and send a frequently interrupted current through them for several minutes. A Leclanché battery will do, with wire of any size from No. 20 to 30. Bar size, steel grade and the way the current is interrupted are not given. Source: Work No. 180 (27 August 1892), p. 382, answers by G. E. B. Picture: our diagram.

初学者

Several minutes (magnetising)

说明

Read the source

"Magnetising by electric induction is effected by winding over the bar several coils of insulated copper wire, and sending a frequently interrupted current of electricity through the coil for several minutes." (Work, 27 August 1892.) For a bar magnet, the answer above it adds: "The current from your Leclanché battery will do, and the wire may be of any size from 20 to 30."

Wind the coil

Wind several coils of insulated copper wire, No. 20 to 30, over the steel bar. Bar size, steel grade and number of turns are not given (unknown); for small magnets the same writer prefers steel of hard temper. Ours: steel bar stock, enamelled copper wire.

此步骤所需材料：

钢棒料1 bar

所需工具：

漆包铜线

未知尺寸

Send an interrupted current

Connect the coil to a Leclanché battery and make and break the current again and again for several minutes. How the current is interrupted is not given (unknown).

所需工具：

电池

漆包铜线

History and honest limits

By single touch, the north end of a permanent magnet is drawn from the middle of the bar to one end a dozen times or more, and the other half is stroked the same way with the south pole; double touch uses two magnets at once from the middle outwards, which is quicker and makes a stronger magnet. Steel bars can also be magnetised by stroking them on the field-magnets of a dynamo. Not given: bar size, steel grade, number of turns, how the current is interrupted.