CBSE Class 12-science Answered

By the larmors theorem An electron subjected only to the force exerted by the nucleus about which it is moving will undergo

larmor precision but no other change in motion when placed in magnetic field.

When a magnetic dipole of moment μ is placed in a magnetic field B, it experiences a torque

which can be expressed in the form of a vector product

For a static magnetic moment or a classical current loop, this torque tends to line up the magnetic moment

with the magnetic field B, so this represents its lowest energy configuration. But if the magnetic moment arises

from the motion of an electron in orbit around a nucleus, the magnetic moment is proportional to the angular momentum

of the electron. The torque exerted then produces a change in angular momentum which is perpendicular to that

angular momentum, causing the magnetic moment to precess around the direction of the magnetic field rather than

settle down in the direction of the magnetic field. This is called Larmor precession.