[SI-LIST] : Magnetic field of a solenoid

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From: Steve Rogers (SRogers@micromill.com)
Date: Fri Dec 08 2000 - 01:41:18 PST


I wish to determine the magnetic field surrounding a solenoid (at any point around the structure). All literature I have consulted (Books re Electromagnetics) give only expressions for the on axis field inside the solenoid or just outside (on axis). All of these fields are derived from Biot and Savart law.

I have seen stated in a number of texts that the external field of a solenoid is zero! I can see this intuitively for a toroid and it may be so for a solenoid that is infinitely long, but what about practical finite size solenoids? Clearly if you connect a coil to a DC power supply set it down on a white sheet of paper and cover it in iron filings you will see lines of force outside the coil!
So there is field outside!!!

The reason for my interest in all of the above is as follows.

I wish to determine the magnetic field surrounding different solenoid structures (different in length to diameter, shape - round or square or what have you).

Any comments ??

Regards,

Steve Rogers
  

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