Why Does Faraday's Law Appear Differently in Various Units?

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SUMMARY

Faraday's Law can be expressed in different forms depending on the unit system used. The two common expressions are: curl(E) = -1/C^2 * ∂B/∂t, which is likely a misprint, and curl(E) = -1/C * ∂B/∂t, which is the correct form in Gaussian or Lorentz-Heaviside units. The confusion arises primarily from the use of SI units versus Gaussian units. The discussion highlights the importance of verifying the source of different expressions, especially in academic contexts.

PREREQUISITES
  • Understanding of electromagnetic theory, specifically Faraday's Law.
  • Familiarity with unit systems, particularly SI and Gaussian units.
  • Basic knowledge of vector calculus, including curl operations.
  • Experience with academic resources in physics, such as lecture notes and textbooks.
NEXT STEPS
  • Research the differences between SI and Gaussian units in electromagnetism.
  • Study the derivation of Faraday's Law in various unit systems.
  • Learn about vector calculus operations, particularly curl and divergence.
  • Examine academic resources that clarify common misconceptions in electromagnetism.
USEFUL FOR

Physics students, educators, and anyone interested in understanding the nuances of electromagnetic theory and unit conversions in physics.

Azelketh
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This is maddening and i cannot find a concise explanation anywhere despite the simplicity of this question.

I keep coming across faradays law expressed as
\text{curl}\left(\mathbf{E}\right) = -\frac{1}{C^2} \frac{\partial\mathbf{B}}{\partial t}<br />
Im only used to working in SI units so all i can do is guess that this is expressed in gaussian units?
and
\text{curl}\left(\mathbf{E}\right) = -\frac{1}{C} \frac{\partial\mathbf{B}}{\partial t}<br />

Can anyone explain these 2 different expressions of faradays law?
 
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Azelketh said:
This is maddening and i cannot find a concise explanation anywhere despite the simplicity of this question.

I keep coming across faradays law expressed as
\text{curl}\left(\mathbf{E}\right) = -\frac{1}{C^2} \frac{\partial\mathbf{B}}{\partial t}<br />
Im only used to working in SI units so all i can do is guess that this is expressed in gaussian units?
and
\text{curl}\left(\mathbf{E}\right) = -\frac{1}{C} \frac{\partial\mathbf{B}}{\partial t}<br />

Can anyone explain these 2 different expressions of faradays law?
The latter uses Gaussian, or Lorentz-Heaviside units. I have to admit to never seeing the former in a general expression for Faraday's law before. Do you have a reference for where you "came across" this form?
 
hmm, the 1/c^2 expression I've only come across once in some lecture slides for uni electromagnetism module. If you've never come it expressed in that form then it could simply be a misprint/error. As the uni course is in recess for summer break here until october it's dificulty in simply asking the lecturer who wrote them. Thanks for clearing that up Hootenanny, i'll just take it as a misprint. :)
 

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