By simple, I mean classroom here. Everybody knows the use of metal filings dispersed on a sheet of paper to visualise the magnetic lines of field but I would like to find a way to measure the amplitude of the field as well. A manner which would not require expensive or hard to provide equipments, ideally as basic as the metal filings trick. I have an idea already: a thin conductive elastic thread under tension. When an electrical current goes through, it should curve and the curvature should be related to the magnetic field. I could not find anything about that subject. Is the idea stupid? Or is it a technique so old that it is not discussed anymore? More to the point, could that be made to work?


I think calculating the magnetic field from such a magneto-torsion measurement might be difficult. Still, that sort of thing was investigated in the mid- to late-1800's by Wiedemann, and then Gore, and maybe many others. In any case, I would recommend using an early form of magnetometer, such as that of Gauss. Conversely, a Hall effect sensor can be used, but this would appear to be more of a black-box sensor to students.

For Gauss' magnetometer, according to his 1832 paper The Intensity of the Earth's Magnetic Forced Reduced to Absolute Measurement, all one needs is a gold wire and a magnetized needle or bar of iron. It's not particulary simple in its interpretation and analysis, but it provides a very good, macroscale detection of magnetic field strength. He mentions that the oscillations of a magnetized needle are commonly used for magnetic field measurements, and improves upon the idea by removing some assumptions with further measurement. Further research would be needed to implement such a device, but it would provide good measurement of the magnetic force at the given point.

There is also the idea of using electromagnetic induction to perform the measurement. With a sufficiently small loop of e.g. copper, moved at a constant rate of speed for a sufficiently small distance, one would be able to approximate the field strength in that region with a multimeter. For a closed loop, measure current, and for an open loop, measure voltage. One may be better suited than the other, depending on expected magnitudes and available instrumentation. I think this would be too difficult, though, without plenty of controlled experiments to verify results. As a general recommendation, look into magnetometers.

Edit: See also this paper if you haven't already.

Second Edit: I think magnetic torsion experiments are more prevalent than I originally thought! Magnetic Torsion by Moreau appears as an abstract in a few periodicals around 1898. Can't find anything more, however.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.