I'm working on an online EECS course, and to be frank some of it is going straight over my head - but at the same time parts of it are far below my current knowledge, so I want to work and stick with it.(adsbygoogle = window.adsbygoogle || []).push({});

The speaker is working through proving current and voltage - to arrive at Kirchoff's laws as far as I can tell (though I haven't got that far).

The first thing that threw me was this talk of 'elements' - does he mean elements as in periodic? Or as in a sub-class of something, a circuit, anything?

He says that a basic rule is defined such that all elements must obey:

[itex]\frac{\delta\phi B}{\delta t} = 0[/itex]

Otherwise they are not allowed, and by doing this it means that the mathematics works out okay, and we can calculate properties easily.

But what does it mean for del phi B by del t to equal 0? What are B and t?

Are they properties of materials that make - say, silicon - suitable for use in electronic circuits?

My second question regards integrating notation. I haven't come across integrals with the following notation yet, and I hope someone can explain:

1) [itex]\oint[/itex]

(ie, what's the difference with the addition of the circle/loop in the center?)

2) [itex]\int_{ab}[/itex] or [itex]\int_{\delta c}[/itex]

(ie, what does it mean to only have a lower limit? Or is the first the lower and second the upper, and in the case of delta c, the limits are the difference represented by the delta - ie if it were say dl, showing extension, the lower limit would be original and the upper the extended length?)

3) [itex]\int\int[/itex] or [itex]\oint\oint[/itex]

(I assume these are for 'second integrals', much like d^2y/dx^2?)

Thanks in advance for any help on either question.

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# Maxwell's, integrals, current, elements, delta phi and confusion

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