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# how can I magnetic distance? Answered

so for the past month my study has been magnets (how do they work) and ive come to electromagnets. what variable/s would affect the distance of a magnetic field. or rather what produces a bigger field, higher voltage, or amperage? thin wire and many wrappings or thicker wire and fewer wrappings. also if anyone knows of any good simulations on electromagnetism they would be much appreciated

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A dipole magnetic field, which is what you produce when you wrap wire around a nail, has a cos(theta) angular dependence, and a 1/r^3 distance dependence.

MAGBOLTZ is one of the best field simulations available, and it's free. You probably want to have some knowledge of Fortran and C++ if you're going to use it.

Looked into MAGBOLTZ because Fortran was my very first computer language and this is evoking pleasant old memories of collage life in basement working a key punch machined:-)

The program seems to work with drift distances for various gas mixtures, only getting to the magnetic fields as a fifth parameter ! ?

BTW ... I'm surprised the field decreases with the coil radius

"1/r^3 distance dependence" can you point me to a source document ?

Wikipedia's article "Magnetic dipole." I've just discovered that this new comment editor does not like having text pasted into it :-(

I haven't tried to paste boilerplate from another source but two or three words get copied and pasted fine on my XP Firefox.

Hi, Iceng. MAGBOLTZ is used for the design of tracking chambers, where charged particles produce ionization, and you want to pick up the ionization electrons by drifting them through E and B fields.

The 1/r^3 dependence for a magnetic dipole is "simple"; see, for exmple,

Ampere-Turns decided the electromagnet strength.

If you use an iron flux guide be it a nail or a 3" diameter bolt shaft you can concentrate as much magnetic flux as the metal can hold, called saturation. When the ampturns create more flux then your metal core saturation can hold the extra flux flows through the surrounding space as best it can and may actually interfere with the desired function..

Keep in mind, doubling the coil turns will also double the wire resistance which will significantly reduce the current flow and increase the heating. That means you will not double the field strength unless you increase the voltage to get that doubling current you want. Understanding that the coil heat power ie Watts is the product of the voltage times the current.

electromagnetic field strength is directly proportional to the strength of the current so double the current, double the electromagnetic field strength. It is also inversely proportional to the distance from the coil, so at double the distance there is half the field strength. The magnetic field strength is also directly proportional to the number of coils, so double the coils, double the magnetic field strength.