Load/Source Impedance

May 09, 2006 20 Replies

I'm not going to say you will ever learn calculus from a few posts in a newsgroup - that's not going to happen - but a couple of things you can keep in mind which might help with things like the above example.

When you see "d(something)/dt" in an equation or textbook, read it as "how quickly (something) is changing" (in time, which is what the "dt" part is about). So "dv/dt" is simply "how quickly voltage (v) is changing."

Also, always keep in mind that whenever you see an equation, it is really just a shorthand way of expressing a concept that COULD be said in plain English (it usually is a lot more efficient to write it out as an equation - in "math language," in other words - but these sorts of things really are just a compact means of describing what's going on). So something like

I = C * dv/dt

isn't just some mysterious collection of symbols, it should be READ as (in this particular case):

"The current through a capacitor (I) depends on how big the capacitor is (its capacitance, C), and how quickly the voltage across it (v) is changing."

A lot longer, but a lot clearer for people who aren't all that comfortable dealing with "the math."

Bob M.

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