Why does a strong magnet always attract a weak one regardless of polarity?

[sachooo]

Recently while working with electromagnet , we noticed one thing.

I we bring strong magnet near very weak PM or electromagnet, It will attract the weak one whatever is the polarity of magnets.

we increased power to electromagnet then it was giving repulsion.

I did't understand this phenomenon can anybody explain this to me.

 

[berkeman]

Recently while working with electromagnet , we noticed one thing.

I we bring strong magnet near very weak PM or electromagnet, It will attract the weak one whatever is the polarity of magnets.

we increased power to electromagnet then it was giving repulsion.

I did't understand this phenomenon can anybody explain this to me.

Welcome to the PF.

What are electromagnets constructed of? You wind wire around what kind of metal?

 

[sachooo]

Welcome to the PF.

What are electromagnets constructed of? You wind wire around what kind of metal?

We used simple mild steel but we observed this behaviour with permanant magnets too.

 

[Vanadium 50]

A strong magnet will attract an ordinary piece of iron. In the case where the weak magnet is very weak, it behaves more like an ordinary piece of iron than a strong magnet.

 

[Dadface]

To express this in more detail I think(but do not know enough about domain theory to be sure)that the field of the stronger magnet temporarily realigns the domains of the weaker magnet such that attraction always occurs.As an example if the N pole of the stronger magnet were brought close to the N pole of the weaker magnet then the domains of the weaker magnet would be flipped round such that its poles reverse.Perhaps if contact was maintained for a long enough time the polarity reversal of the weaker magnet would become permanent.What happens must also depend upon the types of magnets used as well as their strengths.

 

[sachooo]

To express this in more detail I think(but do not know enough about domain theory to be sure)that the field of the stronger magnet temporarily realigns the domains of the weaker magnet such that attraction always occurs.As an example if the N pole of the stronger magnet were brought close to the N pole of the weaker magnet then the domains of the weaker magnet would be flipped round such that its poles reverse.Perhaps if contact was maintained for a long enough time the polarity reversal of the weaker magnet would become permanent.What happens must also depend upon the types of magnets used as well as their strengths.

Thanks You all for this information.

In our project We are trying to attract & repel permanant magnet. To get max force we tried use high power permanant magnet & so we had this problem.
But now I would like know what should be relative strength of both magnets sothat there will be attraction & repulsion both.

Is there any document or book dealing this issue.

Is there any method to measure field strength with multimeter CRO. ( normal electronics Lab instruments )

 

[Dadface]

Hello sachooo.It is relevant to know the difference between "magnetically hard" and "magnetically soft" magnets.I think the Wiki article entitled "magnet" contains all of the information you need and more.