Newbee with a funny question - Page 1
Forum section: electronics / beginners

author: Planobilly
author_rank: Regular Contributor
timestamp: December 05, 2015, 05:35:24 am
content: Hi guys,As a newbee I find a few things in electronics a bit funny.Why do we still insist on describing electron flow as if it were moving from positive to negative? Sorry Ben don't want to hurt your feelings...lol...but then what do you expect from a grown man who likes to fly a kite in electrical storms....lolWhy do we use K when we spell capacitance with a C?OHM's Law...R, ok I get that,V, yep, but I??? who came up with that??Who decided that we should seriously confuse newbee's by having mF and MF and mfd and MFD all mean microfarad?How come it is so hard to find a diagram of a tube socket with pin numbers like you would see it from the top?...lolMe thinks some of these guys from the past been sticking there fingers in to many B+ voltages...lol... A battery and B battery and C battery...really??? when was the last time you used a B battery for plate voltage??...lolThe list could go on for a long while.Cheers,Billy

author: JoeB83
author_rank: Regular Contributor
timestamp: December 05, 2015, 05:57:15 am
content: Traditions tend to stick. It's not just EE and physics that have this problem.

author: Falcon69
author_rank: Super Contributor
timestamp: December 05, 2015, 06:11:26 am
content: he's right, it's not just EE.Take the English language for example. The word "small" has 5 letters, the word "big" has 3......yet, BIG is means larger than small.

author: IanB
author_rank: Super Contributor
timestamp: December 05, 2015, 06:25:05 am
content: OK, I'll bite.Quote from: Planobilly on December 05, 2015, 05:35:24 amIn fact, we don't.QuoteI'm not sure which K you are referring to?QuoteI is for "intensity", as in intensity of current flow. The more intense the current, the hotter your wires will get. C is already taken for capacitance.QuotemF is millifarad (1000 microfarads). µF is microfarad, and MF is megafarad (that's a pretty big capacitor).mfd and MFD are obsolete, you will only see them on old equipment.QuoteWhen you wire a tube socket you solder the wires to the pins underneath as you look at the base, so numbering from the top would not be very helpful.

author: IconicPCB
author_rank: Super Contributor
timestamp: December 05, 2015, 06:41:37 am
content: QuoteCurrent is charge flow.Physicists recognize electron flow from the more negative potential to the less negative potential.The conventional current flow is a relic from early days discoveries in the field of electricity. Electron flow is now understood to be physical reality. Conventional current is strictly incorrect however so longas the two ideas are not mixed in a discussion it makes little difference.

author: IanB
author_rank: Super Contributor
timestamp: December 05, 2015, 06:48:35 am
content: Quote from: IconicPCB on December 05, 2015, 06:41:37 amSo if alpha particles flow from one location to another and increase the positive charge at the destination that is not physical reality?Electric current is just a sign convention, plus vs minus. Nothing more. As long as you keep your sign convention consistent everything will always work out correctly.

author: IconicPCB
author_rank: Super Contributor
timestamp: December 05, 2015, 07:11:54 am
content: Actually electric current is not just a convention. Conventional electric current is ( just a convention).Electrons ( negatively charged particles of certain charge ( please look up physical constants here )), actually get repelled from the more negative potential to wards the less negative potential.Prime example is the mechanism behind the thermionic valve.And yes so long as one is consistent in specifying either conventional or electron flow current then calculations do not go out of kilter.BUT there is a difference between the two flows.

author: rdl
author_rank: Super Contributor
timestamp: December 05, 2015, 03:51:09 pm
content: Personally, I've never understood the insistence on using I for current. C being taken, why not use A? I actually do this myself most of the time when writing notes, maybe because I prefer to use mA for milliamps.

author: Simon
author_rank: Unknown
timestamp: December 05, 2015, 07:19:21 pm
content: The victorians thought they knew everything and decided which way current flows for one reason or another. Not to upset the applecart we have been gracious enough to keep it that way to save rewriting years of textbooks and conventional thinking. for our purposes it does not matter as long as a consistent direction is identified. I tried to look at it "right" for years and it just took longer to understand everything.Not sure we use I and not A but hey ho I got into the habbit eventually.I think I have seem MF used for uF on old parts, it's because in the 60's they did not have the "mu" symbol and must have struct a silent convention that "m" was milli and "M" was micro. While "mu" is available in todays computers many of us use "u" instead as it saves remembering the codes fir "mu" that does not have a keyboard key. I wonder if anyone will ever come up with an "engineers" add on keyboard that carries all of the various symbols used in engineering

author: IanB
author_rank: Super Contributor
timestamp: December 05, 2015, 07:44:44 pm
content: Quote from: Simon on December 05, 2015, 07:19:21 pmI'm not certain, but I think the convention was to write MFD rather than MF. I certainly came across many capacitors in the 70's when taking apart old equipment, both electrolytics from computer power supplies and TV sets and unpolarized capacitors from things like fluorescent tube fittings. MFD is what I recall.

author: Unknown
author_rank: Unknown
timestamp: December 05, 2015, 07:47:16 pm
content: Quote from: Simon on December 05, 2015, 07:19:21 pmI'm now imagining a little USB numpad which contains only engineering symbols and is programmed to spit out the correct character codes instead of having to mess around with "Insert -> special character" all the time

author: Simon
author_rank: Unknown
timestamp: December 05, 2015, 07:58:07 pm
content: Quote from: BulletMagnet83 on December 05, 2015, 07:47:16 pmyea something like that, I'd love one for micro's, ohms and many more

author: onlooker
author_rank: Frequent Contributor
timestamp: December 05, 2015, 08:06:19 pm
content: QuoteAnd many came with no units, just a number such as 0.1, 0.1k or 103k. It turns out, in my case, both 0.1 and 0.1k are 0.1uF and the 103k is 10nF.

author: poot36
author_rank: Frequent Contributor
timestamp: December 06, 2015, 06:53:50 am
content: It might not be the best answer to the keypad add on but the Nintendo 3DS has these symbols º µ ß ƒ ° and a few more on its keyboard under Symbol or More in the keyboard selection area. Kind of weard for Nintendo don't you think? The Wii U may have them to but I have not checked.

author: fubar.gr
author_rank: Unknown
timestamp: December 06, 2015, 07:18:13 am
content: I think Dave said in a recent mailbag video that back in the day there weren't any capacitors in the pico or nano value range.It was uF or nothing!Therefore MFD back then was pretty much unambiguous.

author: retrolefty
author_rank: Super Contributor
timestamp: December 06, 2015, 08:53:56 am
content: Quote from: fubar.gr on December 06, 2015, 07:18:13 amActually in the day it was MFD or uF (E-6) and MMFD or uuF (E-12) or nothing for the condensers, capacitors hadn't been invented yet.That was in the pre-digital days prior to the invention of the ONE bit along with the already existing ZERO bit opened up a whole new fad (or was it opened a whole new fab?)Oh the years have sped by so fast, good thing that speed of light thing has a speed limit.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 06, 2015, 10:04:09 am
content: Quote from: retrolefty on December 06, 2015, 08:53:56 amI can really only speak for Australia,but,"Condenser" was pretty much "dead" as an official term by the mid 1950s.In the same way,picofarads have been around for a long time---you really have to go back to the 1940s & before to seethe consistent use of micromicrofarad.Like everything else,there are transitional periods during which both terms are used,so you sawthe old "uufd" components mixed in equipment with "pf"."Megafarads" or "millifarads" were not realistic units,so "MFD", "MF" (most commonly in electrolytics) or "mf" were used,without fear of confusion.These were really just shortening the word,rather than prefixes,in any case.At least in Oz,non-electrolytics were marked as decimal parts of a microfarad ,so you would see caps marked .0047uf,0.47uf ,& so on,.The transition from pf was usually around 1000pf,Philips tried extending the use of pf to higher values,so you would see such things as 4700pf,& so on,but it pretty much died out.In the 1970s,with the demise of most Australian component manufacturing,"nanofarads" started to appear on imported capacitors.

author: Zero999
author_rank: Super Contributor
timestamp: December 06, 2015, 10:17:01 am
content: Because old drawings and parts used mF for µF, to avoid confusion, milifarads aren't in common use today. Capacitances equal to and above 100mF (100 000µF, 0.1F) are normally given in Farads and below 100mF, µF is used.

author: tggzzz
author_rank: Super Contributor
timestamp: December 06, 2015, 10:22:46 am
content: Quote from: Simon on December 05, 2015, 07:19:21 pmNot really. When the direction of current flow was assigned the whole electricity and magnetism thing was quite mysterious and magical. The electron wasn't discovered until 1897.QuoteOn my keyboard µ is"AltGr-m". There are a few other useful symbols knocking around, e.g.«»¢“”nµæßð?@?e¶????øøþ<>©‘’Nº×÷Æ§Ðª???E®?¥??ØÞ¡?£¼???™±°¿I wonder how many of those will survive the trip through the website and other people's browser!That's a standard DOS keyboard without this "windows key" nonsense, which confuses the hell out of those very helpful people who keep offering to make my PC seem faster.

author: tggzzz
author_rank: Super Contributor
timestamp: December 06, 2015, 10:27:02 am
content: Quote from: vk6zgo on December 06, 2015, 10:04:09 amIf you go back that far you will probably also see capacitors specified in units of Jar, where 1Jar = 1111pF.FFIhttps://en.wikipedia.org/wiki/Jar_%28unit%29