A current-carrying ring is placed inside an ideal solenoid.  When a current is passed through the solenoid

Inside an ideal solenoid the magnetic field is uniform (B) parallel to its axis. A current loop will experience no net force in a uniform field. Magnetic torque ${\tau }_B=MB \sin \theta . If \theta = 0^0 or {180}^0 , {\tau }_{B }is zero , otherwise it is non zero .$ When the ring is held with its plane normal to the axis, two situations can arise as shown below.

Every small segment experiences a radially outward force. Ring has a tendency to expand	Every small segment experiences a radially inward force. Ring has a tendency to contract.