What Is Magnetic Flux and How Is It Measured?

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Magnetic flux refers to the total number of magnetic field lines emanating from a magnet pole, quantified by the equation phi = 4*pi*m, where m represents the strength of the magnetic pole. In Gaussian units, the strength m is measured in gauss-cm², while in SI units, it corresponds to Webers. The discussion highlights that magnetic lines of force typically form closed loops, which leads to confusion regarding the flux through a closed surface around a magnetic pole, especially in the absence of magnetic monopoles. The text being referenced may be oversimplifying the concept by treating one end of a bar magnet as a magnetic pole without accounting for the magnetic field inside the magnet. Overall, the initial explanation in the book may not effectively convey the complexities of magnetic flux and its measurement.
ascky
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I started reading Lectures on Electrical Engineering Vol I, Steinmetz. I thought I should be able to understand most of it, but I don't get the first page! It says that: 'The total number of lines of force issuing from a magnet pole is called its magnetic flux. The magnetic flux, phi, of a magnet pole of strength m is, phi = 4*pi*m '.

What does this mean, and what are the units of m? I thought that because the magnetic lines always formed closed circuits that the flux through a closed surface around a magnetic pole should be zero. I'd really appreciate it if someone could explain this to me.
 
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ascky said:
I started reading Lectures on Electrical Engineering Vol I, Steinmetz. I thought I should be able to understand most of it, but I don't get the first page! It says that: 'The total number of lines of force issuing from a magnet pole is called its magnetic flux. The magnetic flux, phi, of a magnet pole of strength m is, phi = 4*pi*m '.

What does this mean, and what are the units of m? I thought that because the magnetic lines always formed closed circuits that the flux through a closed surface around a magnetic pole should be zero. I'd really appreciate it if someone could explain this to me.
If a magnetic pole existed, the equations for a pole of strength m would by much like those for a charge q.
1. "Magnetic flux" here means \oint{\bf B\cdot dS}.
2. Just like Gauss's law, \oint{\bf B\cdot dS}=4\pi m,
in Gaussian units.
3. In Gaussian units, the units of m would be gauss-cm^2.
In SI units, I think it would be Webers (Whoever he was).
3. "I thought that because the magnetic lines always formed closed circuits...". That is only in the absence of a magnetic monopole.
With magpoles, magnetostatics becomes just like electrostatics.
I suspect your text is using one end of a long bar magnet as an abstraction for a magnetic pole, and not including the B inside the magnet
in finding the flux of 4\pi m.
 
Yes, it seems that this book starts off really badly...
 

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