(a) Prove that for a particle in a potential V(r) the rate of change of the expectation value of the orbital angular momentum L is equal to the expectation value of the torque:

where

(This is the rotational analog to Ehrenfest’s theorem.)
(b) Show that d(L)/dt = 0 for any spherically symmetric potential. (This is one form of the quantum statement of conservation of angular momentum.)

Transcribed Image Text:

d.t (L) = (N).