Both N and S poles exert an attractive force on non-magnetized iron. How does that square with just 2 kinds of poles?
Differences between E and M
It is quite possible to give an object just one kind of charge.
But magnets always come as a package deal: if there's a N pole on one end
of a magnet, there's bound to be a S pole on the other end. If you break
a magnet in half...
A thing that has a north pole but no south pole is called a monopole, but such an object has never been found.
Or if the other pole is brought close:
Now, if you take away the magnet the material is still *kinda* magnetized. There is some remnant magnetization. Notice that most of the little magnets have their dark ends pointing right.
Could mention here: Curie temperature
This is the basis for computer hard disk drives...
Current going in circles
We examined the field around a coil of wire, where the current goes around in circles.
The field looks the same as the field around a magnet:
The modern picture is that all magnetism is caused by small currents--electrons running in circles around their atoms. Sorta like planets orbiting the sun.
An electro-magnet moves about a surface coated with some magnetic material, and gives it a remnant magnet field point one way or the other (these are the '1's and '0's of binary coding).
A rubbed (statically charged) balloon sticks to a wall (which hasn't been rubbed!)
We understand this in terms of an induced charge [PhET]:
The positively charged nuclei of atoms cannot move--they are locked in bonds with their neighbors. But a few of an atom's electrons are free to move.
The electrons will move towards a positively charged object nearby, so the positive object is attracted towards the buildup of negative charge.
The electrons will move away from a negatively charged object, leaving behind a more positive region...which attracts the negative object.
So, either way, there's an attraction!