Maxwell fourth equation incorrect?

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Discussion Overview

The discussion centers around the validity of Maxwell's fourth equation, specifically regarding the inclusion of the displacement current in Ampere's law and the implications for current density in capacitors. Participants explore theoretical aspects, mathematical reasoning, and conceptual clarifications related to electromagnetic fields in AC circuits and capacitors.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions the reasoning behind Maxwell's addition of the displacement current, suggesting that divergence of current density J is zero in a capacitor due to equal current entering and leaving a Gaussian loop.
  • Another participant argues that the current density between capacitor plates is zero, leading to a curl of B that is also zero, which contradicts observed phenomena.
  • A different viewpoint emphasizes that the divergence of J is not always zero, particularly in the context of AC currents, and discusses the implications for the curl of B in relation to the displacement current.
  • One participant requests clarification on whether the divergence of J is zero in capacitors and challenges others to provide proof.
  • A later reply asserts that Maxwell's correction can be derived from the conservation of charge, suggesting that the discussion lacks professional references to support alternative interpretations.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of current density in capacitors and the implications for Maxwell's equations. No consensus is reached regarding the correctness of the fourth equation or the necessity of the displacement current term.

Contextual Notes

Participants highlight limitations in their arguments, including assumptions about current behavior in AC circuits and the mathematical treatment of divergence and curl in electromagnetic theory. The discussion remains open to interpretation and lacks definitive proofs for the claims made.

mdn
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Hi all
this question seems to be silly but i want to where i am wrong. Maxwell was made modification in Amperes law curl H=J and he added new quantity displacement current Jd, reason was that Div.J=0 (true in DC current but not in AC charging capacitor).
but if i say Div J=0 in capacitor because the amount of current entering and leaving is exactly equal in Gaussian loop (loop has half part in space between plate) on the same back direction as it is AC currant and can not flow through capacitor plate, where i am wrong?
and second doubt is that current can not added in series because it is same therefore fourth equation should be
Curl H=2J.
 
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mdn said:
Hi all
...reason was that Div.J=0 (true in DC current but not in AC charging capacitor).
but if i say Div J=0 in capacitor because the amount of current entering and leaving is exactly equal in Gaussian loop (loop has half part in space between plate) on the same back direction as it is AC currant and can not flow through capacitor plate, where i am wrong?

The reason for adding displacement current term into the right-hand side of the equation

$$
\nabla\times \mathbf B = \mu_0 \mathbf j
$$

was that divergence of the left-hand side is zero everywhere for any field ##\mathbf B##, while divergence of ##\mathbf j## is not always zero.
 
The current density between the plates of a capacitor is 0.If you igore dE/dt you get that the curl of B is 0 in this area, and this conflicts with reality.
It's easier to see in integral form, where the curl of B integrated around the boundary of a surface is the same for any surface with the same boundary.
If you take a capacitor you can have one surface going through one of the leads, and another surface going through the gap between the plates. If you integrate only the real current and not the displacement current you won't get the same outcome.
 
div of J is zero or not in case of capacitor? if yes then problem in fourth equation
and if no can you prove?
 
Maxwell's correction to Ampere's law can be derived simply from the conservation of charge. See: http://arxiv.org/abs/physics/0005084

This thread appears to be personal speculation. It is closed unless you can produce a professional reference supporting the alternative form.
 

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