2. A uniform magnetic field exists and it makes an angle with a particle's... · OlympiadBench #1592
Physics · modern-physics
Problem
2. A uniform magnetic field B exists and it makes an angle ϕ with a particle's magnetic moment μ. Due to the torque by the magnetic field, the magnetic moment μ rotates around the field B, which is also known as Larmor precession. Determine the Larmor precession frequency ω0 of the magnetic moment with respect to B=B0k.
Given constants:
All matters in the universe have fundamental properties called spin, besides their mass and charge. Spin is an intrinsic form of angular momentum carried by particles. Despite the fact that quantum mechanics is needed for a full treatment of spin, we can still study the physics of spin using the usual classical formalism. In this problem, we are investigating the influence of magnetic field on spin using its classical analogue.
The classical torque equation of spin is given by
τ=dtdL=μ×B
In this case, the angular momentum L represents the "intrinsic" spin of the particles, μ is the magnetic moment of the particles, and B is magnetic field. The spin of a particle is associated with a magnetic moment via the equation
μ=−γL
where γ is the gyromagnetic ratio.
In this problem, the term "frequency" means angular frequency (rad/s), which is a scalar quantity. All bold letters represent vectors; otherwise they represent scalars.
Part A. Larmor precession
Context question:
1. Prove that the magnitude of magnetic moment μ is always constant under the influence of a magnetic field B. For a special case of stationary (constant) magnetic field, also show that the angle between μ and B is constant.
(Hint: You can use properties of vector products.)
Context answer:
证明题