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# how to make an electromagnet thats a circle be positive on one side and negative on the other? Answered

im basically trying to make an electromagnet that will wrap around a tube of metal and i want to have it magnetize the inside of the metal tube and on the left (as your looking at the tube from the side) its has positive attraction and on the right it has negative push that is my question and if anyone could tell me how i could do this that would be EXTREMELY appreciated... not only that but if i could reverse the polarity so left is negative push and right is positive attraction that would be great to please help its for a science experiment and would be GREATLY appreciated

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A Coil Gun, as Kiteman says?

This is a great video on how to make one:

Magnets do not have "positive and negative", they have north and south poles.

With a coil of wire around a metal tube, there will be a pole at each end of the tube (if the tube is ferrous) or the coil (if the tube is non-ferrous).

The poles will both attract any ferrous metal.

If you want the magnet to push, then the thing you want it to push must also be a magnet, arranged so that either the magnets have both north poles facing each other, or both south poles facing each other.

well i am trying to put a ball into the tube so that the electromagnet wrapped around the outside of the tube will pull the ball inside the tube towards the magnet and once past the magnet will push the ball

Ah, got you!

What you need is to have the coil "on" as the ball moves towards it, then switch off as the ball enters the coil - the ball's own momentum will carry it onwards and out of the tube.

The search term you need is "coil gun":

https://www.instructables.com/howto/coil+gun/

thankyou and also a question i read that mercury is diamagnetic at room temperture and when supercooled to around 4 below kelvin or so becomes superconductive would that mean that at 4 below kelven or even further below would it amplify magnetism if the magnets were on the outside around the tube and the mercury was within? would it amplify the magnetism or reject it?

Diamagnetism has nothing to do with amplification.
And since you won't have a chance get enough mercury or cool it down enough the question is obsolete.
Never mind that the stuff is quite toxic too.
Use bismuth and be happy but don't expect any amplifications...

I'm afraid I don't know ("google is your friend"), but mercury is both expensive and toxic - I wouldn't use it for a coil gun.