For the circuit

Emf introduced in the solenoid,

Where

L is the self-inductance of the solenoid

I is the current in the solenoid.

The direction of the current in the loop is clockwise. When the switch is closed the current will flow in the circuit. Therefore, the current on the solenoid will be increase. Then it will induce a current in the copper ring which is placed along a axis of solenoid. According to Lenz’s law the induced current is such that it opposes the increase in the magnetic field that induces it. So the induce current in the copper ring will be anticlockwise. Because of the opposite direction of the currents the ring will repel. So it will move away from the solenoid.

Horizontal solenoid connected to a battery and a switch. A copper ring is placed on a frictionless track, the axis of the ring being along the axis of the solenoid. As the switch is closed, the ring will move away fro the solenoid.