2 added 24 characters in body edited May 18 '11 at 14:05 Hans de Vries 3,8751717 silver badges2121 bronze badges In the end it is all moving charge. To see that this is also the case for the magnetic field from the spin you need to perform the so-called Gordon decomposition on the charge-current density of the electron as defined by Dirac's equation. see for instance 18.2 in this chapter of my book: http://physics-quest.org/Book_Chapter_Gordon_Decomposition.pdf The Gordon decomposition of the charge-current density of the electron shows an additional part due to the magnetic moment of the electron. This additional part is equivalent to the classical "current from magnetization" given by: $$j=\nabla\times M$$ Where M is the magnetization of the medium. Figure 18.1 of the link above shows how this is just the familiar Stokes theorem in action. The current $$j$$ is an effective current caused by the inherent magnetization of the electron field. This is the current which is the source of the magnetic field due to the magnetic moment of the electron. For Stokes theorem see: http://www.math.umn.edu/~nykamp/m2374/readings/stokesidea/ Regards, Hans In the end it is all moving charge. To see that this is also the case for the magnetic field from the spin you need to perform the so-called Gordon decomposition on the charge-current density of the electron as defined by Dirac's equation. see for instance 18.2 in: http://physics-quest.org/Book_Chapter_Gordon_Decomposition.pdf The Gordon decomposition of the charge-current density of the electron shows an additional part due to the magnetic moment of the electron. This additional part is equivalent to the classical "current from magnetization" given by: $$j=\nabla\times M$$ Where M is the magnetization of the medium. Figure 18.1 of the link above shows how this is just the familiar Stokes theorem in action. The current $$j$$ is an effective current caused by the inherent magnetization of the electron field. This is the current which is the source of the magnetic field due to the magnetic moment of the electron. For Stokes theorem see: http://www.math.umn.edu/~nykamp/m2374/readings/stokesidea/ Regards, Hans In the end it is all moving charge. To see that this is also the case for the magnetic field from the spin you need to perform the so-called Gordon decomposition on the charge-current density of the electron as defined by Dirac's equation. see for instance 18.2 in this chapter of my book: http://physics-quest.org/Book_Chapter_Gordon_Decomposition.pdf The Gordon decomposition of the charge-current density of the electron shows an additional part due to the magnetic moment of the electron. This additional part is equivalent to the classical "current from magnetization" given by: $$j=\nabla\times M$$ Where M is the magnetization of the medium. Figure 18.1 of the link above shows how this is just the familiar Stokes theorem in action. The current $$j$$ is an effective current caused by the inherent magnetization of the electron field. This is the current which is the source of the magnetic field due to the magnetic moment of the electron. For Stokes theorem see: http://www.math.umn.edu/~nykamp/m2374/readings/stokesidea/ Regards, Hans 1 answered May 18 '11 at 3:48 Hans de Vries 3,8751717 silver badges2121 bronze badges In the end it is all moving charge. To see that this is also the case for the magnetic field from the spin you need to perform the so-called Gordon decomposition on the charge-current density of the electron as defined by Dirac's equation. see for instance 18.2 in: http://physics-quest.org/Book_Chapter_Gordon_Decomposition.pdf The Gordon decomposition of the charge-current density of the electron shows an additional part due to the magnetic moment of the electron. This additional part is equivalent to the classical "current from magnetization" given by: $$j=\nabla\times M$$ Where M is the magnetization of the medium. Figure 18.1 of the link above shows how this is just the familiar Stokes theorem in action. The current $$j$$ is an effective current caused by the inherent magnetization of the electron field. This is the current which is the source of the magnetic field due to the magnetic moment of the electron. For Stokes theorem see: http://www.math.umn.edu/~nykamp/m2374/readings/stokesidea/ Regards, Hans