1. E&M II
Griffiths Chapter 8

24. (These quantities are all per unit volume, i.e. densities)

25. Charged cylinder radius a length l inside solenoid

28. In the solenoid. B goes to zero. An E-field is induced.
Field momentum goes away, but total momentum has to be conserved.

29. The induced E-field acts produces a torque on the charged cylinders.
On the outer cylinder
The outer cylinder acquires mechanical angular momentum due to this torque

30. + = Lem Angular momentum is conserved.
Field momentum is fully converted to mechanical momentum.