Permanent Magnet vs. Electromagnet: What's the Difference?

[Xidike]

How compass detect the Earth’s natural magnetic fields, to tell the direction ??

 

[Drakkith]

How compass detect the Earth’s natural magnetic fields, to tell the direction ??

The same way two magnets detect each other.

 

[sophiecentaur]

How compass detect the Earth’s natural magnetic fields, to tell the direction ??

If you won't read that link fully then I don't think you will read any answer I give you. No more spoonfeeding. I'm done.

 

[Xidike]

The same way two magnets detect each other.

Then why the north pole of Earth and north pole of Magnet Does not repel each other.. ?

 

[Drakkith]

Then why the north pole of Earth and north pole of Magnet Does not repel each other.. ?

Because the North pole of the Earth is actually a magnetic SOUTH pole!
(I'm serious)
I think that poles of magnets were named a certain way because one pole wanted to face North all the time. This requires that the other pole, the Earth's pole, be a south pole. I'd bet that way back in the day when magnetism was first studied, they noticed that one pole wanted to face North all the time so they labeled the Earth's pole a NORTH pole since it was in the North, and ignored the fact that the Magnetic pole was actually a magnetic SOUTH pole.

 

[sophiecentaur]

Ahhh. I see your problem and the confusion. The following can be found on the net - I have read it but people don't always bother to make it clear. It confused me at School when I was first taught about magnets. I think many people don't even worry about it at all.

The Correct Name for the 'North Pole' that is marked a magnet is actually a 'North Seeking Pole'. This means it will point to the Earth's North Pole. So this means (annoyingly and confusingly!) that, at the Earth's North Pole, there must be a South Seeking Pole - because that will follow the attraction / repulsion rules for magnets in general!

 

[russ_watters]

Discussion here: http://en.wikipedia.org/wiki/Magnet#Pole_naming_conventions

 

[Xidike]

Is there any condition when Earth And Magnet Repel Each others ??

 

[Drakkith]

Is there any condition when Earth And Magnet Repel Each others ??

Sure, turn the south pole to the north. You have repulsion. It's just REALLY weak.

 

[Xidike]

I tried but it does not work for me..

 

[CWatters]

I tried but it does not work for me..

Rather a lot of people have managed to get it to work including my five year old children.

There is a photo here of the device used to demonstrate the effect..

http://upload.wikimedia.org/wikipedia/commons/5/59/Plastic-compass.jpg

 

[Xidike]

Rather a lot of people have managed to get it to work including my five year old children.

There is a photo here of the device used to demonstrate the effect..

http://upload.wikimedia.org/wikipedia/commons/5/59/Plastic-compass.jpg

They Does not repel.. rather the needle of compass reverses the direction..

 

[CWatters]

Can you explain please.

 

[zoobyshoe]

OK. 'Soft Iron' has very low remanence and makes a very poor permanent magnet. It is also very easily magnetised whist the applied field is there. Perfect when you want to control the magnetic field (solenoid in a starter motor etc. or a relay). Steel is harder to magnetise and will remain magnetised. The right grade of steel of other ferromagnetic alloy is even harder to magnetise and will stay magnetised for longer (impervious to being bashed, for instance).
I don't think Wiki and I disagree, do we? The general term 'iron' doesn't always refer to soft iron but to cast iron, for instanceor 'iron age tools' - which have a higher remanence. You would have found that out if you had read around more, I am certain.

"Iron" refers to the elemental metal, as opposed to an alloy or oxide. Authentic, pure iron will not become permanently magnetised under any circumstances. "Steel" refers to a large variety of alloys of iron, the most common being iron/carbon.

The steels will not become permanently magnetized unless they have been hardened. That's an important point. It is quite possible to rub a piece of soft steel with a magnet or place it in a magnetic field without it becoming permanently magnetized. Tools like screwdrivers and wrenches pick up permanent magnetism very easily because they have been hardened to make them more durable. Motor stators and rotors, on the other hand, are all made of soft steels which do not become permanently magnetized.

Whether or not the steel has been hardened is the make or break condition for turning it into a permanent magnet.

 

[sophiecentaur]

They Does not repel.. rather the needle of compass reverses the direction..

That is hardly surprising if you realize that there are TWO forces acting on the magnetic compass - one on each of its poles.
The 'N Pole' will be attracted to the North and repelled from the South. And the S pole will be attracted to the North and repelled from the South. IFFFFF the magnet suspension will allow it, the magnet will rotate so that it points North-South (the lowest energy situation it can find). Are you telling me this is a total surprise for your?
When we have sorted this out are you intending to give us an equally hard time with Newton's Laws of motion and the Laws of Reflection and Refraction?
Are you just not prepared to THINK at all, for yourself?

 

[Sedilclue]

Well, technically it doesn't matter. However an AC current will alternate the polarity at the frequency of the circuit. So all electromagnets used actually as a magnet to pick up stuff will be DC.

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

I think that AC shouldn't be nice to create a permanent magnet. Am I wrong ?

By other hand no one is telling WHY north and south poles attract. The real WHY i mean, no just a simple human-made law. The law can explain HOW but not why.
Always have thought fields and magnetic lines to be a nice way to explain kids about magnets but I was shocked to see that Meissner phenomena is explain in some places as if magnetic force lines are able to interact each other.
I must say lines don't exist but as a human concept. (All kind of lines... just check em closer)

About permanent magnets i would like to point two things: (For sure tell me if i am wrong)
- Fe(atomic iron) is the most important thing a permanent magnet must have(yes cobalt can be used but quite near in periodic table)
- Any matter with just a kind of atom can not be a permanent magnet (just if my etomic model is right)

 

[sophiecentaur]

The steels will not become permanently magnetized unless they have been hardened. That's an important point. It is quite possible to rub a piece of soft steel with a magnet or place it in a magnetic field without it becoming permanently magnetized. Tools like screwdrivers and wrenches pick up permanent magnetism very easily because they have been hardened to make them more durable. Motor stators and rotors, on the other hand, are all made of soft steels which do not become permanently magnetized.

Whether or not the steel has been hardened is the make or break condition for turning it into a permanent magnet.

I know that steel nails seem to have some remenance (they stay magnetised - for a while, at least) and that many 'steels' cannot be hardened to a useful degree. Are we just talking in terms of a continuum of 'hardness', partly due to the mix and also to the heat treatment? It isn't every steel that can be 'tool-hardened', I'm sure - take 'angle iron', for instance.
I always assumed that transformer laminations were soft iron. Is that true?

 

[zoobyshoe]

I know that steel nails seem to have some remenance (they stay magnetised - for a while, at least) and that many 'steels' cannot be hardened to a useful degree.

This is the case, yes. Nails have been "work hardened" to some degree when the steel wire is taken off the spool, straightened, cut, and the head is formed. You could get a better magnet by completely work hardening a nail by banging down the whole length of it with a hammer on an anvil. This recipe of steel, though, is not intended to be hardened or magnetized, so it will be a poor quality compared to any recipe intended for hardening.

Are we just talking in terms of a continuum of 'hardness', partly due to the mix and also to the heat treatment?

Yes. A totally "soft" steel probably doesn't exist.

It isn't every steel that can be 'tool-hardened', I'm sure - take 'angle iron', for instance.

Right. "Tool steel" has been made according to some specific recipe for the job in question and the heating and quenching to harden it usually has to be tightly controlled for that specific alloy.

"Angle iron" is hot rolled steel. It is formed into that shape by being forced through rollers when it is still glowing hot. It's a soft steel. It can be made harder than it is by heating and quenching or work hardening, but will never be as hard as tool steel.

I always assumed that transformer laminations were soft iron. Is that true?

They developed a special steel alloy for transformers, etc. (It is heat treated to make the crystals larger, but not to harden it.)

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

 

[sophiecentaur]

Thanks for that info. A comprehensive set of answers. The term 'soft iron' seems to be a bit like 'cast iron' in that neither is pure iron - they're just called 'iron'.

 

[zoobyshoe]

Thanks for that info. A comprehensive set of answers. The term 'soft iron' seems to be a bit like 'cast iron' in that neither is pure iron - they're just called 'iron'.

Yes. A lot of literature refers to a "soft iron core" being the proper one for electromagnets. I think what they're mainly trying to get across is that the core has to be 'iron based' and should not be hardened. I'm not sure that anyone ever actually produces pure iron for any practical applications because...

Pure iron is soft (softer than aluminium), but is unobtainable by smelting. The material is significantly hardened and strengthened by impurities from the smelting process, such as carbon. A certain proportion of carbon (between 0.2% and 2.1%) produces steel, which may be up to 1000 times harder than pure iron.

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

 

[Xidike]

What is the direction of Earth magnetic force ?? Vertically Or Horizontally ??

 

[sophiecentaur]

Did you ever look at diagrams of the Earth's magnetic field? Have you connected this with other pictures and descriptions of magnets?

 

[Xidike]

Did you ever look at diagrams of the Earth's magnetic field? Have you connected this with other pictures and descriptions of magnets?

I've searched the Directions of Earth Magnetic field and found that Earth behaves like a gigantic bar magnet

 

[sophiecentaur]

So what does that tell you?

 

[Xidike]

I found that The Earth's real north pole is actually the south pole of it's magnetic field and real south pole is the north pole of it's magnetic field..

 

[Xidike]

A permanent magnet is the one whose electronic domains are aligned in a particular direction as opposed to the iron in which they are scattered and multi-directional. To make a permanent magnet, you can induce magnetism by keepin in close proximity to a magnetic bar or in a magnetic field.

An electromagnet is the one in which magnetic power is induced through electricity. They find applications in generators. Normal magnets do not need any electricity for their magnetism.

What is meant by Electronic Domains ?

 

[sophiecentaur]

What is meant by Electronic Domains ?

Have you read anything at[/PLAIN] this level yet?

or this?

Why do you keep picking one phrase from an answer that you get and, again ask "what is ...?"? Why not google the term and read a few of the links it throws up? Seriously, it gives the impression that you are making no effort for yourself at all.

If you want to have a worthwhile conversation on PF, the best way is to go and find two or three pieces of information elsewhere that seem to contradict or where you can't see the connection and then ask for opinions here. It makes answering worth while for other members.

 

[CWatters]

Sound like a chat bot.

 

[sophiecentaur]

What is a chat bot?
haha

 

[MarkoniF]

What is the direction of Earth magnetic force ?? Vertically Or Horizontally ??

You mean direction of the field lines, not force. There is no force when you are talking about a single object, force is between two objects, and the direction of the force is along the shortest distance between the two, more or less depending on the shape and distribution of the fields.