Well i'm studying this under engineering but its also maths so I posted this here and hope its in the right forum(adsbygoogle = window.adsbygoogle || []).push({});

The question is: When using Gauss's Law i have this equation in my notes: total charge enclosed by surface = closed integral of ( D .ds) over S

the next line (in my notes) equates this to Dr( closed integral of dS over S)

Is this a mathematical manipulation, or is this due to some law? And is Dr just a constant or does it have some meaning? Thanks.

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# Closed integral in electromagnetics

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