How to recognize a polarized magnet

[ChrisGyver]

Hi everyone ,

 

Are there any way to reconize a polarized magnet ? I ask this question because I try to make a little experiment. Make a current with a coil, potentiometer and magnet. Anyway, the schematic is joined with this topic. So, your replies are welcome.

 

( Sorry if my english is bad).

[John Cuthber]

What do you mean by "a polarized magnet "?

[studiot]

All magnets are polarised and have two poles, so try and explain your question more.

 

From the looks of your picture your magnet would work better at right angles to its present position. The poles are usually at the narrow ends and the magnetic field is strongest near the poles.

Edited October 20, 2013 by studiot

[ChrisGyver]

Alright, I got it. I said a mistake. I confused. Regarding the non polarized magnets. That's some objets such as an iron bar which can become a magnet for a short time, when it's in contact with the magnet (Sorry I'm not able to find the link that deal with that issue). In fact, I can't know if my projects work. So, I wondered if my magnet is bad. But it's okay. And now, I want to know if my experiment work. So, what I can do ? I think about oscilloscope but I don't have one. Are they another solutions ?

[studiot]

Hello chris,

 

One problem is that you need to wind a large number of coils to achieve an observable effect without special equipment.

Why are you using an iron bar?

This is normally used to concentrate the magnetic field generated by an electromagnet. You do not gain anything by trying to energise it with a permanent magnet.

In order to generate a voltage you need to take the iron bar away and move your magnet back and fore along the axis of the coil windings.

 

A good apparatus to study this is the inside of an old house doorbell, as in the photo.

 

The white plunger is mounted on a magnet and sent side-to-side when the bell switch is closed allowing current to flow in the coil, generating a magnetic field.

The upright black metal plates are freely mounted so that they vibrate audibly when struck by the plunger, a bit like wind chimes.

 

I have removed the batteries for clarity. You can also create a voltage at the terminals by manually moving the plunger side-to-side. this can be measured with a voltmeter or used to illuminate a small bulb (not an LED).

 

Edited October 20, 2013 by studiot

[ChrisGyver]

I use the iron bar to wind the coil. As I saw from some examples about this experiment. So, I only use the potentiometer, a larger coil and the magnet without the iron bar.

[Sensei]

Are there any way to reconize a polarized magnet ?

Do you want to find out where your magnet has N and where has S?

 

You can do it using compass.

http://en.wikipedia.org/wiki/Compass

 

If you don't have it, you can create it in a couple seconds.

You will just need f.e. glass of water and needle (in minimum version).

Move your magnet in straight direction on needle to magnetize it.

After that other needles will start attaching to it.

Then carefully place on water. If done properly it won't sink (if sink use magnet to take it from water and repeat).

Some people attach something unsinkable to needle, but IMHO it's degrading speed in which needle will react.

Now you can rotate your magnet in hand, and see how compass is also rotating synchronously.

The stronger magnet you have, from longer distance you will be able to rotate or change direction of compass.

 

You can make array of compasses and see magnetic field lines.

 

Once I had 20+ such homemade compasses in whole apartment

Funny thing, none pointed the right direction to Earth's N-S.

Too many electronic equipment.

The only unaffected place is here balcony.

 

You can verify this at 12:00 looking at Sun, compass should be pointing one end to Sun, and 2nd end in Earth's north.

[studiot]

Sensei has offered a good method of studying the magnet, but not the electric part.

However, have a care here.

 

The point of the compass needle that points to the Earth's North Pole is actually the south pole of the compass needle magnet.

 

It is often called a 'north seeking pole' as a result.

 

The part of the Wiki article called "how a magnetic compass works" explains this.

Edited October 20, 2013 by studiot

[ChrisGyver]

ok thanks for your replies. I'll come back to you if i need more advices.