Angular momentum in circular motion is the product of the linear momentum of the particle and the radius of rotation:
$$L = pR = mvR$$
where,
R— distance from the axis of rotation to the point where the force is applied (m);
p— momentum (N·s);
m— mass of the body (kg);
v— velocity (m/s).
The law of conservation of angular momentum states that when there is no external torque present in the system, then its total angular momentum remains conserved.