Question

two main uses of solenoid

Answer 1

Solenoids  used as electromagnets.
Solenoids can be used to slow the flow of electricity in a circuit

Answer 2

    Solenoids are good electromagnets.  They are used in automatic locks (door locks for example).  They are used in circuit breakers to protect equipment.  Solenoids have inductive nature.  The introduce delay in electric circuits.  They can be used for adjustment of power factor.  Solenoids are used to store energy in the magnetic field.