1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can we spin something to get electric without magnet or piezo?

  1. Jun 12, 2013 #1
    Permanent magnet can degenerate by many ways. But it really needed in compact generator to convert mechanical force into electric

    But are there any other way to generate electric from mechanical force without magnet?

    I want to design self exited magnet for dynamo. It need tobe an effect that could generate electricity from spinning something and feed electric to excite the electromagnet as a starter, when electromagnet become magnetized it would then feed itself after that

    Are there any effect like I talk about?
    Piezoelectric cannot be used. It's short spark electric so it need to have inconvenient circuit
    I have heard that there are such a way like spinning the conductor (copper/silver) and it would generate electric directly from centrifugal force pushing electron. But I'm not sure it's true and really useable in this case or not. Or there are any other effect I could use?

    Thank you

    P.S Another question
    What happen when we weave the coil around permanent magnet, using permanent magnet like it is electromagnet, and feed electric into it. Would it stronger? Would it regenerate magnetic force? Or would it make that magnet degenerate faster?
  2. jcsd
  3. Jun 12, 2013 #2
    What you describe is the common dynamo or generator---more than 100 years old, and still used for most generators because cheaper than using permanent magnets for the field. Part of the output from the armature is run thru the field coil, either in parallel or in series. It starts up from the very small residual magnetism which is present in any piece of iron. The current from the armature reinforces this and the field rapidly builds up until the iron pole pieces 'saturate'.
    In the case of an ac generator or 'alternator', the current must be rectified to make dc to drive the field coil. There's one in every car. Look up 'dynamo' or 'generator' in any book or online.
    Your last question: the current can make the magnet either stronger or weaker, depending on the direction of current flow.
  4. Jun 13, 2013 #3
    You mean the effect that could generate electric from non magnet is common?
    What is that effect? Are there any name?

    And if the current flow is same direction as magnet, so make it stronger, are there any side effect? Could it regenerate magnet? Could it degenerate magnet?
  5. Jun 13, 2013 #4
    It's actually kinda simple , if you don't have a permanent magnet you use two coils one which is in the stator and the other one goes into the rotor where the magnet would have been or vice versa doesn't really matter , because the physical law goes like if you have a conductor that is being passed through (cuts through) magnetic field lines it induces electric current into the conductor.

    The only difference why they will put magnets in the rotor not the stator because then you wouldn't need a commutator which is a part of electric motor that wears out first usually.
    Now if you don't have a magnet you have two wires ones are spinning ones are stationary , put some current through one set of those wires and they will generate EM force now spin the other set of wires through that force and voula !! you have induced current.

    As other members said already too bad but this is nothing new it is being used for many many years (old as the world) :)

    Want to understand how generators work look up electric motor , as they are basically the same.But if you came up with this idea by yourself not knowing all the work that has been put into it before that is not bad , that shows you have some intuitive thinking , continue to read and learn and maybe you will come up with a truly new idea one day.
  6. Jun 13, 2013 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member


  7. Jun 13, 2013 #6
    What I want is to not have magnet and any electric power as a stator. I need plain neutral object or box that was not magnet but when spin it can generate electricity without any presence of magnet. To feed the electromagnet when there are no electric anywhere to feed as stator

    So you just not read it carefully
  8. Jun 13, 2013 #7


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    that description really doesnt make much sense. It is somewhat difficult understanding what you are trying to say.
    But that said ... as others have stated.... You need metal, be it a copper wire or whatever moving in a magnetic field to generate a voltage ( current )

  9. Jun 13, 2013 #8
    The duality of electromagnetism is going to make you hard if you don't want to generate a field.
  10. Jun 13, 2013 #9
    Without any presence of magnet meant no magnetic field anywhere. You should see that I talk about piezo so I should know that very basic. If it so basic just as your taught why I need to ask. You think I'm that much stupid?

    I just talk about self excites magnet why do you think I am so stupid to not know normal dynamo work? Or you don't know what is self excites magnet???

    As I said. I want any effect which can generate electricity from spinning "WITHOUT ANY PRESENCE OF MAGNET"
  11. Jun 13, 2013 #10
    It's not about I don't want. I just want to design the tool in situation that we cannot acquire magnet or electricity anywhere. The permanent magnet inside dynamo could be degenerated completely. So I want to make dynamo with self excited magnet. Still it need some little magnet or electric before start it

    So it would be easier if we would have thing that can generate electricity even very little to be an embedded starter for this kind of dynamo. We would spin a free waste work to produce a little electric but when it could start magnetize dynamo then the system would need just outside force and not need the starter

    Piezoelectric crystal may be an option. But it harder to put it in
  12. Jun 13, 2013 #11
    mmm i see!

    and static energy? you can try
  13. Jun 13, 2013 #12
    you shouldn't be angry about someone not knowing you also now knowing your level of knowledge assuming you don't know some things.That is not a matter of a stride rather a matter of discussion of ones knowledge level.

    As for the self started generator it is already possible to start it with a small magnet as you say and then applying more torque and increasing rpm you can build up the power output and also feed the generator self excited coil to keep up the field strength so that the generator would function , still this is already done and is not a new idea that is all I wanted to tell you in the first place.No need to get upset.
  14. Jun 13, 2013 #13


    User Avatar

    Staff: Mentor

    I remember being told that residual magnetism of the core is enough to excite the generator, so you don't need anything more.
  15. Jun 13, 2013 #14
    Because I think residual magnetism could be degenerate too. Especially in bicycle or any kind of moving engine under the Sun. there are always heat and vibration to destroy magnetism before component
    So I want some trick that could always start the system again even residual magnetism is gone

    And Crazymechanic. I got annoyed because you just spill nonsense without reading anything I said carefully. Even your last comment is also proved that YOU NEVER READ ANYTHING CAREFULLY just want to spill your knowledge
  16. Jun 13, 2013 #15


    User Avatar

    Staff: Mentor

    http://en.wikipedia.org/wiki/Excitation_(magnetic [Broken])
    Last edited by a moderator: May 6, 2017
  17. Jun 13, 2013 #16
    Well if elementary physical laws or phenomenon are nonsense to you then I don't know what else I could "spill", my drinks on the floor I guess while trying to understand what you have written in your posts. :D:D

    Ok don't take it personally , just a joke. I admit I had a problem understanding what you really wanted in the first place but now things are getting more clear.
    And by the way, I don't think you should be afraid that a metal could loose it's most basic properties like magnetism under normal atmospheric conditions.
    Even typical ferrite magnets keep their magnetism for longer than one lives , if not exposed to fire or mechanical damage or something else.
    So I think sunlight on a bike considering the generator is in some kind of casing plastic or other wouldn't do any harm , I don't think that is a problem here. :)
  18. Jun 13, 2013 #17


    Staff: Mentor

    You cannot produce a current without a magnetic field.

    Others have explained how you can produce a current without permanent magnets, but to produce it without any magnetic field anywhere is impossible.

    Don't get mad at people for not reading carefully when you did not write clearly to begin with. I understand that you probably have a language barrier, but that means that you need to be understanding also and accept that most communications with you will require some clarification before others understand what you are asking. This thread is closed.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Can we spin something to get electric without magnet or piezo?
  1. Can we spin air? (Replies: 14)