Strange form of Gauss' Law

In summary, the conversation discusses the use of Gauss's Law and different unit systems in the derivation of E=(2kλ)/r for an infinite line of charge. The expert recommends the use of Gaussian or rationalized cgs units for a more elegant and intuitive understanding of electromagnetism at the graduate level.
  • #1
stephen8686
42
5
I was looking for a derivation of E=(2kλ)/r for an infinite line of charge. I understood that you need to use Gauss's Law and a cylinder around the line. When looked it up, I found this: http://www.vizitsolutions.com/portfolio/gausslaw/lineCharge.html
He starts out with ∫E⋅dA=4πq. I have never seen Gauss's Law shown like this and am not sure how it is equivalent. Can someone please show me how he got 4πq from Q/ε0?
 
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  • #2
stephen8686 said:
I was looking for a derivation of E=(2kλ)/r for an infinite line of charge. I understood that you need to use Gauss's Law and a cylinder around the line. When looked it up, I found this: http://www.vizitsolutions.com/portfolio/gausslaw/lineCharge.html
He starts out with ∫E⋅dA=4πq. I have never seen Gauss's Law shown like this and am not sure how it is equivalent. Can someone please show me how he got 4πq from Q/ε0?

That is what is known as a form of Maxwell equation in "Gaussian units".

http://www.physicspages.com/2014/11/06/electromagnetism-in-gaussian-cgs-units/

Zz.
 
  • #3
Wow, I didn't even know that was a thing! Thanks. Are CGS units commonly used in Electricity and magnetism?
 
  • #4
stephen8686 said:
Wow, I didn't even know that was a thing! Thanks. Are CGS units commonly used in Electricity and magnetism?

Yes, and in fact, if you go on to take graduate level E&M and use the infamous Jackson's Classical Electromagnetism text, that was all written in cgs units.

Zz.
 
  • #5
Well thanks a lot for the help!
 
  • #6
ZapperZ said:
Yes, and in fact, if you go on to take graduate level E&M and use the infamous Jackson's Classical Electromagnetism text, that was all written in cgs units.

Zz.
Well, and this in my opinion not infamous but rightfully famous text (in fact I think it's the best traditionally written textbook on the subject and I don't understand why anybody takes the effort to write more such traditional E&M textbooks at the graduate level when you can as well use Jackson) got worse with the 3rd edition when switching from Gaussian (the 2nd best choice of units; the best one are rationalized cgs units, aka Heaviside-Lorentz units) to SI units. Electromagnetism looses all it's elegance and physics intuition by writing it down in SI units, which are very useful for practical but very ugly for theoretical purposes :-).
 

1. What is "Strange form of Gauss' Law"?

The "Strange form of Gauss' Law" is a modified version of the traditional Gauss' Law in electromagnetism. It takes into account the effects of time-varying magnetic fields on electric fields, which are not considered in the original form of Gauss' Law.

2. How is the "Strange form of Gauss' Law" different from the traditional Gauss' Law?

The traditional Gauss' Law only applies to static electric fields, while the "Strange form of Gauss' Law" takes into account the effects of time-varying magnetic fields on electric fields. This results in a more comprehensive understanding of the relationship between electric and magnetic fields.

3. What is the significance of the "Strange form of Gauss' Law"?

The "Strange form of Gauss' Law" allows for a more complete understanding of the behavior of electric and magnetic fields. It is particularly useful in studying electromagnetic waves and the propagation of energy through space.

4. How is the "Strange form of Gauss' Law" derived?

The "Strange form of Gauss' Law" is derived from Maxwell's equations, which describe the behavior of electric and magnetic fields. It is a result of modifying the original Gauss' Law to incorporate the effects of time-varying magnetic fields.

5. What are some practical applications of the "Strange form of Gauss' Law"?

The "Strange form of Gauss' Law" has many practical applications, including in the design of antennas, radar systems, and wireless communication devices. It is also used in the study of electromagnetic interference and the behavior of electromagnetic waves in different mediums.

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