a. An electron moves in a uniform magnetic field around a circle. Any other circle is drawn through it, the OO′ axis of which is directed along the magnetic field. Show that the sum of M + 2π1 eΦ, where Φ is the magnetic field flux through this circle, and M is the electron angular momentum relative to the OO′ axis, does not depend on the electron position.
b. Show that the sum of M + 2π1 eΦ does not change in the case of the motion of an electron in a uniform magnetic field along a helical line.
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