Animation shows the angular momentum vector of a particle (m) moving round a circular path of radius R at V about a point on the axis of the circle
The red vector is the linear momentum vector (p), the blue vector is the position vector (r) and the black vector is the angular momentum vector ( L ).
The relation between the vectors is L = r × p
The green and magenta vectors are the axial and radial components of the angular momentum vector and have magnitudes of mvR and mvh respectively.
Notice that during the rotation of the particle the axial component of angular momentum remains unchanged and the radial component rotates at the same angular speed as the particle itself.
Experiment by changing the height of the reference point above the plane of the circle, the radius of the circle and the angular velocity of the particle.