How to change the polarity of a core coil magnet?

Question

Electronics

Good afternoon, tell the carduelis a couple of nuances
Rotors el. motor have winding and core, the same or not?
It’s just that in my practice it didn’t work out to make a pole magnet from a coil with a core, it comes out a permanent magnet of all poles.
How does the polarity change occur in those coils, or is there a special core that has nothing to do with the magnetic flux and only for a fixed attachment for winding? (if so, what are they made of).

Answer 1

I tried to wind the coil on the bolt, it only began to attract the magnet, without repelling one of the poles, although everything is fine without the bolt, 2 poles - it can both attract one and repel the other.
The question arose of how to make a coil with a core that would not only attract, but also repel the opposite pole with the other side.

1. A clean (not magnetized) piece of iron is equally attracted by a powerful magnet from both its ends - with N, with S. There is no repulsion.
2. If this piece of iron is weakly magnetized, then its field will not overcome the field of an external strong magnet, and it will still be attracted from both ends. But from opposite poles - a little stronger than in paragraph 1, since the fields are summed up, and from the same poles - a little weaker, since this weak field acts against a strong external field. Those. there will be no repulsion, but there will be a difference in the force of attraction.
3. Magnets of comparable strength already allow you to get a normal repulsion.
4. There is no difference whether the magnetic field is received with the help of a coil with a current, or a piece of iron is magnetized by itself - all the same, the interaction of these field sources will be as described in p2.
5. So, in order to get a repulsion from a nail with a coil wound around it, it is necessary to pass a strong current through it in order to get a strong magnetic field.

Answer 2

Rotors motor have winding and core, the same or not?

Not always.
Reversal of polarity (direction of current)

Answer 3

Can you describe what you want to get? Because the question is kind of weird. Another perpetual motion machine? :)
Any magnet has two poles N and S. They (the poles) will both attract metal , but interact differently with similar poles of other magnets (different poles attract, the same repel).
The reversal of the electromagnet polarity is achieved by simply reversing the polarity of the voltage across the winding.