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![]() "art" wrote in message s.com... On 10 Mar, 06:41, "Dave" wrote: "art" wrote in message oups.com... On 9 Mar, 22:13, (John E. Davis) wrote: On Fri, 09 Mar 2007 16:45:31 GMT, Dave wrote: Gauss' Law is for static electric charges and fields. It is usually used for problems in electrostatics, but it is not confined to such problems. The differential form of it is just one of the Maxwell equations: div E(x,t) = 4\pi\rho(x,t) Integrate it over a fixed surface and you get the integral form, which is Gauss's law. It is valid with time-dependent charge densities and time-dependent electric fields. --John John, you have hit it on the nose. It is the logic that is important and that logic applies for a resonant array in situ inside a closed border whether time is variant or otherwise. The importantant point of the underlying logic that all inside the arbitary border must be in equilibrium at the cessation of time because the issue is not the static particles but of the flux. Period Thus the very reason for a conservative field in that it is able to project static particles in terms of time if time was added. For static particles time is not involved therefore ALL vectors are of ZERO length and direction is an asumption based on the action if and when time is added. John, you included time but did not mention time variant, was this for a reason? I have specifically use time variance since that enclosed within the border is an array in equilibrium from which the conservative field is drawn from. I am so pleased that some one came along that concentrated on the logic and not the retoric and abuse. Art he may have hit what you believe correctly.. but unfortunately it is not a valid generalization. as i stated in my other message: no, i'm afraid you can't just put a 't' on each side and have it make sense in the general case. time varying charge implies a current, a current implies a magnetic field, then you have to include Ampere's law and add curl(E)=-dB/dt to the mix. while you may be able to constrain the changes in rho(t) to some short time or constant current and eliminate the dB/dt part of the problem, that would only apply in specific conditions, not to the general case.- Hide quoted text - - Show quoted text - Thats O.K. David, The appeal made for this thread was for people outside of America since eamericans were more interested in other things and I am assuming the Gentleman is from outside America. This discussion in the past has been bedeviled with arraogance and abuse to the neglect of logic, this has been the mode of this group for a very long time. If there was not such derision you could have looked up Gaussian law on the web where you would have found the mathematics behind the logic. If you had done this you would have found that curl is a part of the mathematical underpinning that in the event of time that part of the equation is zero. If time was part o0f the logic then you insert the value of curl in the equation, look up curl for your self and place it in the original equation which you are not changing i.e. concentrate on the mathematics and the underlying logic and the result becomes apparent.( and I have stated as such in past threads) you obviously have not read and understood my recent posts. when you do curl of electric fields you get ampere's law which takes into account the time varying electric field... but of course also brings in the magnetic field that is related to it. unless you add that part into the equation you are ignoring half of the effects and will never get the proper understanding of the equations. simply adding time to gauss's equation, written either in differential or integral form simply ignores the magnetic field part and the effects of curl and the resulting field and wave propagation effects that must be taken into account when you start talking about time varying fields. |
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