Can someone explain Gauss' Law for Magnetism

[rockyshephear]

Vanadium. If you know what is remotely close to true, would you please share it?
Thanks

 

[Vanadium 50]

Why don't you take a look at a textbook? Purcell is a good one.

 

[rockyshephear]

Is it that complicated to explain in a few sentences?

 

[Nick Bruno]

wow, that was a long list to read thru.

I may have some insite, but its probably elementary compared to what everyone was talking about.

when you have nabla dot B = 0 this is indicating the divergence is zero, or in other words, what goes in comes back out. This is true for any arbitrary surface or volume.

There is no such thing as a magnetic monopole like in electricity (positive or neg charged particles), so only dipoles exist (pairs of sources and sinks). This means the magnetic field wraps around on itself. The field lines have a direction from positive to negative.

Now, what actually makes a magnet work I am not too sure. I think its the rotation of atoms and their polarity (when they are all aligned a certain way) hence the term magnetic moment when describing magnetization? Not sure, but this is definitley an interesting topic and thought Id thro in my two cents. Thanks.

 

[rockyshephear]

Thanks for that. I understand now, that the divergence is zero and that what goes out comes back in. I think divergence is probably a misnomer. I like 'netfluxthroughput' better. lol Much more descriptive. Divergence seems to imply things separating as a function of time.
So if Nabla dot B = 0, tell me a physical case where Nabla dot (something) =1. This would imply that much enters a volume and nothing ever leaves. Black hole? lol
Nabla dot black hole=1 Sorry for being flip but I'm exhausted from trying to get a lay explanation for this.

 

[Nick Bruno]

an example where the divergence is not zero would be an electrically charged particle.

Say you have a positivley charged atom, this serves as a source of an electric field. The field emits in all directions. put a control volume around this particle and ur divergence is larger than one because you have more coming out then going in. --> nabla dot E = q ; where E = electric field and q = electric charge.

Another example would be the end of a garden hose. When you put a control volume around the end, water is coming out and it is acting as a source. No water is entering the control volume.

Its all really dependent of what you choose your control volume to be and if there are items within the contol volume that cancel out your sources, such as a water drain or a negativley charged particle.

And yes, i think there is speculation that black holes may be magnetic monopoles. this gets into string theory and stuff, but I am not too sure about all that.

 

[rockyshephear]

Thanks.