# Motion of a magnet inside a solenoid

I have a homework problem where a bar magnet is placed halfway inside a horizontal solenoid. A cut away shows that the magnet's north pole points to the left of the page and the south pole is outside the solenoid. The coils of the solenoid point into the page on the top, and come out of the page from the bottom. The problem asks how the magnet will move when the power is turned on and current flows through the solenoid.

Using the right hand rule with my thumb pointing along the wire, I have found that the field due to the solenoid points to the left (the arrow in red), so the magnet will be pulled in that direction. I am unsure whether the magnet will shoot out the end of the solenoid, or if it will sit in the middle. I understand the magnetic field drops off outside the solenoid, so there would be no force moving it, but I am inclined to think the magnet's momentum could keep it moving, and it will leave the solenoid. A lab partner told me I could think of the ends of the solenoid as magnetic poles, so the magnet would reach equilibrium in the middle. Could someone tell me what will happen to the magnet and why?

• Inertia will keep it going. Mar 6, 2020 at 4:12