The given simple field equation is valid for long solenoids, almost exactly for length >= 100*radius. There's also a simple equation for the field at the centre line of short (radius < length) and a slightly more complicated formula for medium length coils. See e.g. https://en.m.wikipedia.org/wiki/Solenoid
Field of a flat coil can be calculated by summing the contribution of each loop.
According to the text from where you took the above picture, the general formula seems rather this one:
View attachment 153911
Which is not for the average field, but the field at some specific radius z.
This video tutorial just confirms the above formula as being the general case at any radius:
https://slideplayer.com/slide/9159072/
Refers to 00:35s to be more specific.
z is the distance from the coil center plane along the axis.I want to calculate the field with that formula but i don't understand what z is.
Z is only mentioned in "where the coil is centered at z=0"...
z is the distance from the coil center plane along the axis.
Before we discuss about suitable coil geometry, you should tell more clearly about the purpose of your design. For a short coil, maximum field strength is only achieved in the center point of the coil (r=0, z = 0). What's the working volume where you want to achieve a certain field strength? How uniform?
The center of the coil is just a point. My question was about the operating volume, let's say a Zylinder of radius r1 and height h where the axial field strength doesn't drop below a certain values.Like i said i need 0.4T or more in the CENTER of the coil.
The center of the coil is just a point. My question was about the operating volume, let's say a Zylinder of radius r1 and height h where the axial field strength doesn't drop below a certain values.
20A into 2 ohms means 800W power dissipation, the heat of a small cooking plate.
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Tesla bifilar configuration as I know it has some effects on self capacitance but absolute none on DC field strength. https://en.wikipedia.org/wiki/Bifilar_coil
No, you are saying this for the first time. You only told about 4 cm inner coil diameter, which can have many purposes, not about field distribution.I repeat again field must be inside the 4cm inner diameter of the coil.
.How uniform? I'm not sure what you mean, clearly it cannot be perfectly uniform if we look at lines of force inside such coil. So as uniform as it gets
I don't recognize the video showing anything.Why do you say "absolute none on DC field strength" when i just posted a vid showing ~30% increase in field strength by using Tesla bifilar config.
O.K., that can be used as a specification. Don't care about uniformity, only specify the minimal field strength. I may sound pedantic, but is the 0.4T field magnitude (any direction) or axial field strength?Field must be 0.4T or more in that center region 4cm wide and let's say 1cm high.
No, you are saying this for the first time. You only told about 4 cm inner coil diameter, which can have many purposes, not about field distribution.
I believe my question was much more precise than your witty answer.
You are asking for an optimal coil form (diameter, length, number of layers) for a given wire length. The optimization problem can be solved if you give us a performance metric.
I don't recognize the video showing anything.
O.K., that can be used as a specification. Don't care about uniformity, only specify the minimal field strength. I may sound pedantic, but is the 0.4T field magnitude (any direction) or axial field strength?
Video claims, it doesn't show, small but important difference. If a video "shows" a new over-unity apparatus, do you believe?Video shows how field gets ~30% stronger when winding is in Tesla bifilar config, i don't know how you missed that.
Let's please just focus on what is the best configuration to achieve 0.4T field in the center of the coil with given parameters (or variants of them).
Field must be 0.4T or more in that center region
I already tried a similar calculator for flat coil.
https://kaizerpowerelectronics.dk/calculators/spiral-coil-calculator/
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