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Thread: what is change in the magnetic flux (delta B)?

  1. #1 what is change in the magnetic flux (delta B)? 
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    What is change in the magnetic flux (delta B)? Like on this site.


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    I think it is the magnetic field lines coming out of the bar magnet moving in relation to the loop as a result of moving the loop over the magnet. They have to move for a current to exist.


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  4. #3  
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    The rate of change of flux is a function of the strength of the magnet, it's distance from the measuring point (presumably the coil) and it's rate of motion, the size and shape of the coil and the magnet.

    Have a look at 'maxwell's field equations'
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    Is it like, when I approach magnet, than the magnetic domains of the coil get in line with the magnetic field of the magnet and when I get back the magnet, the magnetic domains of the coil are like in the first position? I mean the direction of the magnetic flux.
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    Can somebody help me to determine the direction of the magnetic flux of the coil?is that, something to do with the aligning of the magnetic domains?
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    Go and look up Flemming's left and right hand rules, in this case I think you will need to pay particular attention to his right hand rule (generator) whereas the left hand rule is for a motor.
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    Quote Originally Posted by Megabrain
    Go and look up Flemming's left and right hand rules, in this case I think you will need to pay particular attention to his right hand rule (generator) whereas the left hand rule is for a motor.
    I sow that, but not any particular information, got from there.
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  9. #8  
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    Well that is the pertinent rule, that will tell you which way the lines of magnetic flux become orientated and which way the current will flow maxwell's equations will give you the details BUT you cannot just jump in at the deep end, this is a very very complex subject, there is insufficient data to satisfy the requirements for maxwell's equations.


    http://en.wikipedia.org/wiki/Fleming's_right_hand_rule
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    Quote Originally Posted by Megabrain
    Well that is the pertinent rule, that will tell you which way the lines of magnetic flux become orientated and which way the current will flow maxwell's equations will give you the details BUT you cannot just jump in at the deep end, this is a very very complex subject, there is insufficient data to satisfy the requirements for maxwell's equations.


    http://en.wikipedia.org/wiki/Fleming's_right_hand_rule
    Ok, I already know that.
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  11. #10  
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    Can somebody tell me how to determine the direction of the magnetic flux of the coil?
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  12. #11  
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    I believe its directly perpendicular to the flow of the current.

    here is what my rule says in my old college text book.

    If a circular loop of current carrying wire is grasped with the right hand so the fingers are curled in the direction of the current the magnetic field direction inside the circular area formed by the loop is the direction in which the extended thumb points.

    which would be perpendicular to the coil.
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    That is Flemmings Right hand law, you really should read up on it and practice it if it is important to you, tell me why do you want to know the answer to your question?
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    Quote Originally Posted by Megabrain
    That is Flemmings Right hand law, you really should read up on it and practice it if it is important to you, tell me why do you want to know the answer to your question?
    I want to know, why it is like that? Why it is like the Flemming's right hand law? What happens inside the structure of the coil?
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  15. #14  
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    That my friend, is a question only God could answer.

    When it comes to atoms we simply do not know 'why' for anything about them except that 'they do'
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    Quote Originally Posted by Megabrain
    That my friend, is a question only God could answer.

    When it comes to atoms we simply do not know 'why' for anything about them except that 'they do'
    And can you please explain me this quote from "Newton Ask A scientist"
    These days, most hula hoops have beads in them. Let's pretend that if
    the beads move inside the hoop they will generate wind through the hoop.
    Let's say if they go clockwise, they generate a wind going in the direction
    a screw would go if the beads were turning it. Let's say if you increase
    the amount of air going in that same direction through the hoop, the beads
    will feel forced to move (so far we have Faraday's law) counter-clockwise
    (now we've added Lenz's law).
    How is it possible that increasing the amount of air will change the direction of the beads?
    Here is the whole topic:
    http://www.newton.dep.anl.gov/askasc...9/phy99x61.htm
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  17. #16  
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    Quote Originally Posted by scientist91
    And can you please explain me this quote from "Newton Ask A scientist"
    IT is not fair to expect me to explain the writings of others, if you do not understand what they have written then you should contact them direct, I have forgotton more than I remember on this subject and have tried to help you by pointing you to other areas of study. Maybe one of our other members might be able to help?

    Lenz'z law only states [along the lines of] that the emf induced in the coil creates a magnetic field in opposition to the original field.

    To save me writing it all up (and possibly making errors) then finding you say 'I don't understand' you must research it for yourself, Just type in 'laws of mmagnetism' and you will then be able to start reading.

    There is a book called 'A Dictionary of Named Effects and Laws' (in chemistry physics and mathematics) by D.W.G Ballentyne and D.R.Lovett
    I have a copy of the third (1972 ed) search Amazon to see if there is a later edition or whether you can purchase a second hand copy.
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  18. #17  
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    Quote Originally Posted by Megabrain
    Quote Originally Posted by scientist91
    And can you please explain me this quote from "Newton Ask A scientist"
    IT is not fair to expect me to explain the writings of others, if you do not understand what they have written then you should contact them direct, I have forgotton more than I remember on this subject and have tried to help you by pointing you to other areas of study. Maybe one of our other members might be able to help?

    Lenz'z law only states [along the lines of] that the emf induced in the coil creates a magnetic field in opposition to the original field.

    To save me writing it all up (and possibly making errors) then finding you say 'I don't understand' you must research it for yourself, Just type in 'laws of mmagnetism' and you will then be able to start reading.

    There is a book called 'A Dictionary of Named Effects and Laws' (in chemistry physics and mathematics) by D.W.G Ballentyne and D.R.Lovett
    I have a copy of the third (1972 ed) search Amazon to see if there is a later edition or whether you can purchase a second hand copy.
    But nowhere writes, how the magnetic flux of the permanent magnet changes.
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  19. #18  
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    So far as I remember the 'flux' does not in normal circumstances change for a permanent magnet, hence the name 'permanent' magnet.
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  20. #19  
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    Permanent magnets can be de magnetized though. I beleive heating an object to its Curie Temperature destroys the magnetism of a permanent magnet. Its something like 700 degrees C, for iron.
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