[morzh]

Rod,

I think what confuses some folls is, "this paper is a special kind of paper, it is impregnated with special compounds and oils".
Heck yeah, papyrus, that is some of the docs written on it, have survived for thousands of years. Though I would not use that one for making capacitors.

Paul,

My son says I am a very bad teacher. The reason is, I (I actually have my education in physics and part of it was, they were prepping us for being teachers in schools; and during the practice I was singled out as the best of the group) am very methodical in my explanation. Borderline (sometimes downright) droning. And, I require my student to know his basics, as without it there is no teaching any further; so when the student (son/daughter, as I do not teach otherwise) simply wants me to solve the problem or do shortcuts, I refuse.
Perhaps, because of this my being methodical, though lengthy, my writing sometimes is easy to understand as I do not skip things without which that, what is being explained, would not be able to be understood.

PS. English being my second language helps. I try not to (though I can) make the language excessively flowery or studded with idioms. That is, when I explain things. My way is, I am actually explaining it to myself as to a dumb/fresh student. If I am satisfied, then I put it out.
PPS. O. Henry is my favourite (well, one of the favourite) writer, and, knowing what real writing is like, I will spare the literature buffs from the throes of reading my verbal diarrhoea.



Roy,

My version of "blunt" is, I do not beat about the bush, trying to tell what I think and at the same time not to hurt anyone's feelings, when we are talking about facts, not the tastes.
The facts like, well 1) Ohm's law is the law, 2) Perpetuum Mobile is not possible, 3) paper capacitors from 30s today are a device which is physically different from what it was when it left the factory, 4) pure socialism/communism is not economically viable, and such.
Facts cannot hurt. Unless one tries to fight the facts.


As for the electrolytic caps, you are right, employing them at well below their max ratings prolongs life by orders of magnitude.
Roughly, the life of the cap DOUBLES every 10 degrees Kelvin (or C, same thing) dropping below the rated maximum. Think of it. If your rated temp is 105C and you bring it down to 65C, you prolong your cap's rated 2,000 hrs 16 times. 32,000 hrs. You have to run your set for 1hr for 100 years every day to meet this. And then there is also the Voltage factor. Which is, if it has effect, can be the Rated to Applied ratio to the degree up to 5. So, when you use your cap, rated at 500V, at 250V, 2.5 to the degree up to 5 (almost a 100) which is what you multiply your 32,000 hrs by. That is, 3,200,000 hrs. This thing will leave longer then us and our children, and grandchildren, combined. Of course, this is the first approximation.

And, another advantage of Voltage derating, though this is for ceramic MLCC caps: their capacitance at rated voltage could drop as far as to mere 10% of their nominal one. So, if you think you have an X5R 100uF cap rated at 6.3V and you use it to decouple (and as bulk) for 5V, you might have mere 15uF left.

Live with it now