# Homework Help: Physical interpretation of the equation (time derivative of Spin angular momentum)

1. Apr 15, 2012

### hangainlover

1. The problem statement, all variables and given/known data
$d\hat{S}/dt = γ\hat{S} \times \hat{B}$
What is the physical interpretation of this equation i.e. what is the behavior of the magnetic moment in
an uniform magnetic field?

2. Relevant equations

I dont think I need any equation for this, just intuition or vector calculus identity?

3. The attempt at a solution

The original question asked me to derive that equation by drawing analogy with classical system.
I said $d\hat{L}/dt =\tau= d\hat{S}/dt= γ\hat{S} \times \hat{B}$
Thats fine, but i have hard time seeig what this means to magnetic moment (gamma S)

(plus do you guys know why it suddenly doesnt show up in latex mode?)

2. Apr 15, 2012

### hangainlover

Re: physical interpretation of the equation (time derivative of Spin angular momentum

Also, I know angular momentum L is not even close to being spin momentum S, but for some reason my TA said thats how you look at it. if anyone can justify this...