Possible Error in Vector Calculus Book

AI Thread Summary
The discussion highlights potential errors in the treatment of Maxwell's equations in a vector calculus textbook by Jerrold E. Marsden and Anthony J. Tromba. Key concerns include the incorrect labeling of the magnetic field H as magnetization and issues with the representation of the equations, particularly regarding the divergence of D and B. The conversation notes that terminology for magnetic fields varies across different texts, leading to confusion. It also emphasizes that in practical physics, H is directly controlled through currents, while E is created using potentials. Overall, the book may prioritize mathematical representation over physical accuracy.
Dahaka14
Messages
73
Reaction score
0
There is a section that contains dealings with Maxwell's equations in my vector calc book, and there are, to my belief, numerous errors. Some of them I am certain on, but the is one I am not so sure on, although it would be a bigger blunder.

The book describes Maxwell's equations as, having E as electric field and H magnetic field:
\nabla\cdotE=\rho
\nabla\cdotH=0
\nabla\timesE+\partialB/\partialt=0
\nabla\timesH-\partialD/\partialt=J

Aside from current density J not being bold due to being a vector, from what I know if one wishes to write maxwell's equations without using constants, they must be written:
\nabla\cdotD=\rho
\nabla\cdotB=0
\nabla\timesE+\partialB/\partialt=0
\nabla\timesH-\partialD/\partialt=J

Second, they defined H as magnetic field, when it is magnetization. Is there something wrong here?
 
Physics news on Phys.org
It would help if you named the book and author thereof.
The book is probably using "Heaviside units", which are rationalized without the
epsilonzero and muzero. You should use \cdot to get the divergence right.
You are right about the D and B in the first two equations.
The names given to B and H vary widely among different books.
Some books call H "magnetic field", others call B "magnetic field".
I prefer the term for B, which is the physical magnetic equivalent of E.
The names used for B are even more varied and confusing.
"Magnetization" is always used for the magnetic moment per unit volume
(to within varying factors of 4 pi). In your units, it would equal M=B-H.
Your book probably just wants to demonstrate the math, and doesn't care much about the physics.
 
Sorry about the LaTex, it's the first time I've ever used it. I had the /cdot in before, but I must've deleted it while trying to make it look better.
The book is Vector Calculus (5th Edition) by Jerrold E. Marsden and Anthony J. Tromba.
Actually, I just noticed, the dot is there at the upper right corner of the del, but I DID have it look like a divergence before as aforementioned.
 
Last edited:
In a lab setting, physicists deals with the H field and the E field. This is because we use currents to create a magnetic field, and H is what we control directly. That is, B is dependent on H, but we can always directly control H. However, we use potentials to create an electric field directly.
 
Thread 'Question about pressure of a liquid'
I am looking at pressure in liquids and I am testing my idea. The vertical tube is 100m, the contraption is filled with water. The vertical tube is very thin(maybe 1mm^2 cross section). The area of the base is ~100m^2. Will he top half be launched in the air if suddenly it cracked?- assuming its light enough. I want to test my idea that if I had a thin long ruber tube that I lifted up, then the pressure at "red lines" will be high and that the $force = pressure * area$ would be massive...
I feel it should be solvable we just need to find a perfect pattern, and there will be a general pattern since the forces acting are based on a single function, so..... you can't actually say it is unsolvable right? Cause imaging 3 bodies actually existed somwhere in this universe then nature isn't gonna wait till we predict it! And yea I have checked in many places that tiny changes cause large changes so it becomes chaos........ but still I just can't accept that it is impossible to solve...
Back
Top