Will a solenoid inside another solenoid increase its strength?

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Discussion Overview

The discussion revolves around whether placing a solenoid inside another solenoid can increase the overall magnetic field strength. Participants explore theoretical and practical aspects of this concept, including the use of air and iron cores, and the implications of the superposition principle in magnetic fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions if nesting solenoids can double the magnetic field strength from 1 Tesla to 2 Tesla, given specific parameters like core material and dimensions.
  • Another participant asserts that placing solenoids inside each other can increase strength, but only if they are connected in a series or parallel configuration that aids the magnetic field.
  • A participant introduces the superposition principle, suggesting that magnetic inductions may add vectorially when applying Ampere's law.
  • Another participant notes that while fields inside nested air-core solenoids add, iron's nonlinearity and saturation limit the effectiveness of this approach, indicating that gains in field strength may be minimal once saturation is reached.
  • A reference is made to the National Magnet Lab's use of hybrid technology, which employs two coils, one inside the other, to achieve high magnetic fields.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of nesting solenoids, with some supporting the idea that it can increase strength under certain conditions, while others highlight limitations due to material properties and saturation effects. The discussion remains unresolved regarding the exact impact on field strength.

Contextual Notes

Participants mention specific parameters such as core material, dimensions, and current, but the implications of these factors on the magnetic field strength are not fully resolved. The discussion also touches on the complexities of magnetic field interactions, particularly in nonlinear materials like iron.

Matt01
Will placing a solenoid inside another solenoid increase it's over all strength?

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 let's 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 if it would reach 2 tesla.)
 
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Matt01 said:
Will placing a solenoid inside another solenoid increase it's over all strength?
Yes, but only if they are connected in series/parallel-aiding fashion.
 
Last edited:
What do you know about the superposition principle?
 
Nothing. I received another message and I'll share it with you citing the superposition principle. I am getting ready to dive into it.

"The short answer to your question is that you can increase
7_69e3966668f4dabe833bedf0903ccb0c.png
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"."
 
So i found this while looking into the superposition principle:



The question is since one is inside the other, would I still need to take into account the vectors or does the math simplify to B total = B1+B2?
 
The fields inside nested air-core solenoids add. Iron is highly nonlinear and once it reaches saturation, gains are small. (1T is far beyond iron's saturation induction.) So yes, field strength increases, but no, it's not simple superposition.
 
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