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18.1 Magnetism

 

The Walter Fendt simulation enables you to plot the field lines around the magnet.© Walter Fendt. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

The PhET simulation allows you to explore the interactions between a compass and a bar magnet. You may vary the magnet's strength, see how things change both inside and outside the magnet and use the field meter to measure how the magnetic field changes. You can also investigate magnetic field around the Earth.

Further information on the Earth's magnetic field, including how it is affected by the solar wind, may be found in  from the British Geological Survey website.

The Earth's magnetic field is a lot more complicated than that suggested by the simple dipole model shown in Figure 18.6 of Understanding Physics. Furthermore, it changes slowly over time as indicated in the map of changing historical declination below (from the US Geological Survey — for more details see the Wikipedia entry on ).

Wikipedia gif

Understanding Physics

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Mansfield and O'Sullivan, Understanding Physics, 3rd ed., John Wiley & Sons, Chichester (2020),

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