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Electrical Engineering/Using a permanent magnet for the core in an electromagnet

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QUESTION: Hi Cleggsan,

How are you? I hope you are genki.
I have been researching something, and I am wondering if you could help me clear something up, as the information I have found is not very definite.
I am interested in what would happen if a permanent magnet were to be used as the core in an electromagnet. I want to increase the strength of the magnet. Would it be possible to increase the strength of a permanent magnet by winding copper wire around it and putting current through the copper coil?
I have searched for this topic on some forums and some people say it is possible, others that it is not. Still others say the increase would be miniscule/negligible. It is hard to get a definite answer.
If this is possible, would the increase of the strength be tiny, or would it be possible to produce a marked increase in field strength? Would the field strength drop back to its original level once the current going through the copper coil has been stopped?

Appreciative as always. Arigato gozaimasu.

Best regards,
Eddie

ANSWER: Yes, a hybrid combination is possible. I don't know the mathematics of it but the coil around the permanent magnet may become shielded in some regards.  But, the principle of the permanent magnet biasing the solenoid such that a small amount of electrical input is necessary to complete the action would be a viable concept in my view.  Does this answer adequately?  

Domo

PS: Hai, genki-des



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Permanent magnet as electromagnet core
Permanent magnet as el  
QUESTION: Thanks Cleggsan!

I am always happy when I get an answer telling me something is possible!
Can I just confirm that I have understood correctly? In the attached image I have drawn the permanent magnet with the copper coil around it. I have drawn the basic field lines for the permanent magnet on the left, and for the permanent magnet plus electromagnet on the right.  Is this about right?
I am also wondering if you can suggest how I might go about calculating the combined magnetic field? I have a formula for calculating the strength of an electromagnet -
Magnetic field = permeability x turn density x current
but I am wondering what I should key in for the permeability value in this situation? Would it be the same as usual?
Would calculating the combined field of the permanent magnet and the electromagnet be something like -
permanent magnet's level of gauss plus electromagnet's gauss (permeability x turn density x current) or do you think there would be some other factor I would need to take into account.

Thanks again for your answer,
Stay genki!

Answer
I can't be sure what the diagrams mean.  The lines of force are shown but you don't distinguish between lines from the permanent magnet and the coil.  Also, I am not certain where the solenoid piston is located and where the movement takes place nor how much linear movement you are expecting.

But, seems you are heading the right direction.  Keep plugging away.  Masugo.  

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cleggsan

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All technical areas of Electronics Engineering.

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BSEE, MBA, Design, R&D, University Research.
Senior Life Member of IEEE. Life Fellow of AES.

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IEEE, Consumer Electronics Society, Audio Engineering Society.
Broad teaching experience; work experience mostly in consumer electronics and conversion from analog to digital technologies. Pioneer in digital audio at all levels.

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BSEE (Equiv) BYU BSEE University of North Dakota MSBA (MBA) Illinois State University Graduate Studies in Computer Science - Bradley University Graduate Studies - Ohio University Graduate Studies - University of Missouri Kansas City DeVry Tech - Electronics

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