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Query about why there is a torque on this spinning ring in a magnetic field

We learnt in class that the $\vec m\times \vec B$ is the torque of a current loop in a magnetic field. I was trying to understand this by considering the diagram above. Let the B field be pointing in ...
2
votes
1answer
1k views

Magnetic Dipole Moment

I've been trying to tackle this problem for more than a day now, and would appreciate some help. The problem is to prove that the magnetic dipole moment of a spherical ball of mass $m$ and charge $Q$, ...
1
vote
1answer
565 views

Classically, why is the gyromagnetic ratio always $q/2m$? [duplicate]

For uniform charge and mass distribution for a rigid body rotating with a uniform angular velocity about its centre of mass, I want to know if it is just a mathematical artifact of integration which ...
2
votes
2answers
148 views

Current loop and direction ambiguity of the magnetic moment

Consider a circular loop in the XY-plane which carries a current $I$. Then it behaves as a magnetic dipole with moment $\textbf{m}=I\int d\textbf{S}$ where $\int d\textbf{S}$ is the area of the loop ...
8
votes
2answers
20k views

Relation between magnetic moment and angular momentum — classic theory

How do I prove the relation between the vectors of magnetic moment $\vec\mu$ and angular momentum $\vec L$, $$\vec\mu=\gamma\vec L$$ ? Many text books and lecture notes about the principles of ...