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MacM

New Member
Hi,

I'm new here. I'm almost 63 years old and have had the privelege of working at the frontiers of science most of my adult life. I enjoy it very much. I have had specialized education and experience via the US Army and a special act of Congress and have received 4 years equivelent College in mechanical, electrical and nuclear engineering with specality training and post graduate training in Process Control Instrumention Systems. i.e. electronics, hydraulics and pneumatics. My MOS was 52K20, that is a Nuclear Reactor Operator-Process Control Instrumentation Specialist.

We were involved in the development of the commercialization of nuclear power. That is the peaceful use of atomic power.

I have a minor but very annoying problem. I am on another MSB and have managed to draw a detractor that follows me around trying to phoo-phoo or claim I don't know what I am talking about, regardless of subject matter and claims to be an experts himself.

The following is an example of his tatics. It involves a highschool student that posted a topic called "Batteries and Capacitors". In it he has made some statements that were lets say a bit strange and I tried to provide helpful information at his level of understadning, but also knowing this individual would likely follow me there, I added some caveats to note that my post was for all practical purposes but that there were exceptions and I noted some of them.

Please take time to scan these extracts to see what I mean. What I am looking for would be anybody with electronics knowledge and/or experience that might provde feedback, which I may re-post regarding this persons inaccuracy or impropriety with respect to his claims in relation to the topic at hand.

Thanks for your consideration.



Student Poster: (Topic Batteries and Capacitors)
******************************************************
Make circuits with a battery, a capacitor, and a flash bulb. The flash bulb connected to the battery alone will not flash. The flash bulb connected before the capacitor will not flash. The flash bulb connected after the capacitor will flash from the burst of energy unleashed from the capacitor. When you have found the circuit that operates the flash bulb, you know which terminal current flows from.

You can do a similar determination with fuses. You might find a fuse that will not blow when connected to the battery alone but will blow when placed in series after a capacitor. In that case, place fuses on either side of the capacitor. The side the fuse blows is the side current flows into.

***********************************************************

My Response What?

I am amazed by the above test descriptions. They seem wholly un-real. Did you actually get these from some place?

Current in a series circuit is the same on either side of a capacitor. The current is high initially and slows down to a full charge in about 7 RC time constants.


Student Poster:

**********************************************************
Look at the circuit in a disposable camera. How is the capacitor arranged with the flash bulb?

If you don't like using capacitors, just use two fuses, three wires and a battery. Select fuses that will blow when current from the battery runs through them. Connect the fuses in series. The fuse that blows first is closest to the terminal that current flows from.

***********************************************************

My Detractors Post Attacking my Reply to the Student:
REF: Current in a series circuit is the same on either side of a capacitor. The current is high initially and slows down to a full charge in about 7 RC time constants.


Not quite. The wave output of the capacitor lags behind the wave input. It takes time for the water being poured in to make the water coming out change speed.


My REPLY:
You dropped the ball on this one. The phase shift (or wave as you call it) is voltage. If you apply a voltage across a capacitor the current leads the voltage but for all ((practical purposes)) series current is series current. What goes in comes out.

There is an extremely minor caveat however to that and just to insure that you are not once again trying to be one-upsman since it is in response to my post,. Let me spell it out for you.

Ideally my above statement is correct in theory, and for every pragmatic application you can think of, but at the physics level no component is perfect or ideal.

Hence a capacitor will also have not only some resistance but also inductance. Any resistance would have no affect on the series current issue. The inductance however combined with the capacitance gets into a gray area where I wouldn't make absolute statements, although as said for all practical purposes my statement is valid. See Thevenin's Theorem and Kirchhoff's Laws

The amount of unavoidable inductance in a capacitor is called "relative specific inductive capacitance" (epsilon r) ('er' here since I don't have symbols) or better recognized as "Dielectric Coefficient" and it has to do with the magnetic permeability of space vacuum. It has a value of mu = 4 pi/10E7 henries/meter based on the rationalized mks system.

Where epsilon o ('eo' here) and c = 1/(mu*eo)^.5; which yields

eo = 1/(36*PiE9) farads/meter as an approximation. er tables must be used if specific results are required.

The er tables provide data to account for what is called "electric absorbtion" or Dielectric Hysteresis. It is this phenomena that causes a capacitor to heat up under dynamic AC signal conditions.

It would be this component that provides a very negligable drop in the series current law.

Voltage lags current in a capacitor and current lags voltage in an inductor. But the voltage lag does not cause a drop in current flow between input and output.

Input and output are always equal (except for the dielectric hysteresis which can be ignored). To consider it would be like considering the affects of Relativity on a kid riding a bicycle down the road.

Therefore I see your post as not knowing the difference in current laws and voltage laws and functions of various electronic components or circuit design.


My Detractors Response: (hereafter I shall refer to Me and Him)

ME: See Thevin's Theorm:

Him: Only applies to resistors, and does therefore not matter here.

ME: ANS:Untrue statement as shown from Esbauch attachment of Thevinin's Theorem and AC Circuits
Attachment: ac circuit.gif (An extract from Esbauch showing Thevenin's Theorem being used in AC Circuits)

Him: Show me 1 case that uses Thevenin's Theorem to deal with anything besides resistors

Me: ANS: I did, see above

Him: As for your scanned page, it doens't show anything except simplifying, you can never use thevenoin's theorem to reduce a capacitor out of a system. That is what I said, and it is still true.

Me: ANS:Your posts are all over the place. You never mentioned "reducing" a capacitor out of a system except in this closing wrong statement.

Him: I was explaining why it refers to DC as well. You are the one who asked. If you already knew, you should not have asked.


Me: My post clearly show I was aware of transient affects (In Rush current) and dielectric hysteresis.

So then tell us of anyother cause for a lag (phase shift) between in/out current from a DC (Battery) circuit.


Me: No d_mn way you design anything electronic. You simply haven't shown any understanding of circuitry.

Him: What exactly haven't I shown an understanding of? You seem to think I actually sit there and put stuff together. I do design, not assembly. I haven't used this since the test I memorized it for. (I highlited this for your edification)

Me: What phrase does one memorize to remember the color codes?

Him: bad boys (take) our girls but violet goes willingly

Me: Based on these responses I will grant you SOME knowledge of electronics be it exposure or school would be hard to tell but it appears you are rusty as hell and certainly are no expert.

bad boys rape other YOUNG girls but violet goes willingly
l......r.......e.......r........e..........r.......l.....i.........r........h
a....o.......d......a.........l..........e......u....o........a........i
c....w...............n.........l..........e......e....l.........y........t
k....n...............g.........o.........n............e.................e
.......................e........w.......................t

0....1......2.......3........4..........5......6...7........8........9

You forgot #4 (Yellow). What, we can't say rape here?

The bottom line is you introduced AC circuitry as a challenge to a DC topic and you have attempted to claim I don't know what I'm talking about by making claims of things that are irrelevant to the topic and that I had mentioned in my post before your posts, just to insure you wouldn't come back with such minor irrelevant crap and you do it anyway. What is it with you.

((And he concludes with this bit in answer for another example of current lag in a DC circuit. I'll grant you that the cap might cause some imeasurable lag but for DC series circuits it is not a practical concern. High frequency AC certainly))


Him: Since you only asked one question, lag is also effected by:
(electrolytic caps)
the electrode solution interface
the electrolyte being used
(Dielectric)
thickness
ion mobility

***********************************************************************

Any helpful comments to deal with this twit would be appreciated. It doesn't matter what I say he keeps moving the goal post and making new claims and charges. Others are just setting on the sidelines watching.

You can e-mail me at [email protected]



Thanks.

MacM
 

pebe

Member
Don't waste your time with him! You won't change people like that - they were born with arrogance in their genes.

His mind is made up - so don't confuse him with the facts.
 

MacM

New Member
Pebe,

Thanks.
 
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