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Thread: Will placing a solenoid inside another solenoid increase it's over all strength?

  1. #1 Will placing a solenoid inside another solenoid increase it's over all strength? 
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    While doing research into solenoids I came across the MagLab (The National High Magnetic Field Laboratory) where they place coils one inside another to bolster the field, and reach upwards of 45 Tesla. They use an air core, high number of turns, and 30 mw to achieve this.
    (Note: I know that no material can achieve any way near 45 Tesla. looking to increase the field strength of realistically week fields. )
    My question is, can the same be done for iron cores?

    Example:

    All aspects of the cores will be the same except the Diameters and internal geometry/volume.

    Length of 12 inches/304.8mm

    300 turns

    relative permeability of the core is 5000

    .2 amp

    1 Tesla lets say will be the max field strength.

    The first rod has a diameter of 2 inches/50.8mm

    with wiring and insulation it's total diameter is 2.5 inches/64 mm

    The second iron rod has a diameter of 4.5 inches/114.3mm

    From the center of the second we remove 2.5 inches/ 64mm and bore straight though the iron rod essentially creating a pipe so we can place the first solenoid inside the second one. The length has not increased both are still 12 inches/304.8mm. There would be a very small amount of air the the field would pass though due to the second solenoid occupying the space.

    Could this method work in increasing the field strength from 1 Tesla to 2 Tesla?
    Would there be any increase in the strength of the combined solenoids?
    Is there a way to determine what the increase would be if there is one?
    (Note: Wondering what the strength would be at the end face. )
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  2. #2  
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    Quote Originally Posted by Matt01 View Post
    While doing research into solenoids I came across the MagLab (The National High Magnetic Field Laboratory) where they place coils one inside another to bolster the field, and reach upwards of 45 Tesla. They use an air core, high number of turns, and 30 mw to achieve this.
    (Note: I know that no material can achieve any way near 45 Tesla. looking to increase the field strength of realistically week fields. )
    My question is, can the same be done for iron cores?

    Example:

    All aspects of the cores will be the same except the Diameters and internal geometry/volume.

    Length of 12 inches/304.8mm

    300 turns

    relative permeability of the core is 5000

    .2 amp

    1 Tesla lets say will be the max field strength.

    The first rod has a diameter of 2 inches/50.8mm

    with wiring and insulation it's total diameter is 2.5 inches/64 mm

    The second iron rod has a diameter of 4.5 inches/114.3mm

    From the center of the second we remove 2.5 inches/ 64mm and bore straight though the iron rod essentially creating a pipe so we can place the first solenoid inside the second one. The length has not increased both are still 12 inches/304.8mm. There would be a very small amount of air the the field would pass though due to the second solenoid occupying the space.

    Could this method work in increasing the field strength from 1 Tesla to 2 Tesla?
    Would there be any increase in the strength of the combined solenoids?
    Is there a way to determine what the increase would be if there is one?
    (Note: Wondering what the strength would be at the end face. )
    The short answer to your question is that you can increase but not for the reasons you think. If you put a solenoid inside another solenoid and you apply Ampere's law, you will find that the magnetic inductions add vectorially. The effect is known as "superposition of effects".
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  3. #3  
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    AndrewC,

    Thanks for the reply. I will look it over in a few hours after I wake up.

    Regards,

    Matt
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  4. #4  
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    Quote Originally Posted by Matt01 View Post
    While doing research into solenoids I came across the MagLab (The National High Magnetic Field Laboratory) where they place coils one inside another to bolster the field, and reach upwards of 45 Tesla. They use an air core, high number of turns, and 30 mw to achieve this....

    Could this method work in increasing the field strength from 1 Tesla to 2 Tesla?
    Would there be any increase in the strength of the combined solenoids?
    Is there a way to determine what the increase would be if there is one?
    (Note: Wondering what the strength would be at the end face. )
    Your method will fail at the upper field strengths you cite because of the limited saturation flux density of iron (around 1.5T, depending on how the iron has been formed). Above Bsat, the core is effectively absent.
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  5. #5  
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    Yes the method will fail at the upper field strengths, however that is not the goal. The goal is to fully saturate a solenoid to its upper limit so with iron depending on it, as you correctly point out say of 1.5 T. Then inserting it into what will be anther solenoid. The iron will be hollow so that the first solenoid can be placed inside of it. I want to fully saturate the second to say 1.5 T if possible and try to achieve 3 T as far as the over all field strength is concerned. I know i can never reach 45 T, but that is not the goal. I wondering if even though the iron will max out at a saturation of 1.5 T if the fields they make can bolster each other for a higher over all field strength and in this case would be 3 T. AndrewC points out it may be possible. Feed back is always welcomed and most appreciated.

    "The short answer to your question is that you can increase but not for the reasons you think. If you put a solenoid inside another solenoid and you apply Ampere's law, you will find that the magnetic inductions add vectorially. The effect is known as "superposition of effects".


    Best regards,
    Matt
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  6. #6  
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    Quote Originally Posted by Matt01 View Post
    Yes the method will fail at the upper field strengths, however that is not the goal. The goal is to fully saturate a solenoid to its upper limit so with iron depending on it, as you correctly point out say of 1.5 T. Then inserting it into what will be anther solenoid. The iron will be hollow so that the first solenoid can be placed inside of it. I want to fully saturate the second to say 1.5 T if possible and try to achieve 3 T as far as the over all field strength is concerned. I know i can never reach 45 T, but that is not the goal. I wondering if even though the iron will max out at a saturation of 1.5 T if the fields they make can bolster each other for a higher over all field strength and in this case would be 3 T. AndrewC points out it may be possible. Feed back is always welcomed and most appreciated.

    "The short answer to your question is that you can increase but not for the reasons you think. If you put a solenoid inside another solenoid and you apply Ampere's law, you will find that the magnetic inductions add vectorially. The effect is known as "superposition of effects".


    Best regards,
    Matt
    Putting one solenoid inside another solenoid has the same effect as adding up the number of coils
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