Question

Consider a solenoid connected to DC power supply such that magnetic field is pointing out of

the solenoid on the end that is facing you.

a) A metal bar about 50% longer than the solenoid is inserted halfway into the solenoid.

Does the metal bar experience any force from the solenoid?

b) If so, in what direction?

c) With the metal bar removed, if you were to attempt insert a bar magnet from the

solenoid side where the magnetic field is going outward, North end first, what force, if any,

would it experience?

d) What if the bar magnet is inserted South end first?

Answer 1

By placing a metal core inside a Solenoid it's magnetic field increases. Because of Lenz's law, while inserting the metal bar the Solenoid will try to counter the net effect by exerting a force directed so that the metal is expelled.  

Inside the Solenoid the magnetic field lines go from south to north, so if we insert the bar magnet where the magnetic field is going outward with the North end first, they will repel, while if we insert the south end first they will be attracted