Why do we use I for Amps in Ohms equation? - Page 1
Forum section: electronics / beginners

author: vulturebetrayer
author_rank: Contributor
timestamp: September 15, 2016, 12:44:51 am
content: Why do we use I for Amps in Ohms equation?This is one of the hardest parts for me learning Ohms law as I always confuse what the I is for.I have banged it into my head that I is amps, but I do have dyslexia and that makes it difficult if there is no word to associate with the I.I have googled this and all I ever find are descriptions of Ohms law but can't find a damn thing on why current is I.It just bugs the hell out of me.

author: rfeecs
author_rank: Frequent Contributor
timestamp: September 15, 2016, 12:55:23 am
content: From Wikipedia:https://en.wikipedia.org/wiki/Electric_currentQuote

author: vulturebetrayer
author_rank: Contributor
timestamp: September 15, 2016, 01:12:04 am
content: Quote from: rfeecs on September 15, 2016, 12:55:23 amthanks, not sure how I missed this in wikipediafor anyone else:TLDR: INTENSITY of CURRENT

author: JS
author_rank: Frequent Contributor
timestamp: September 15, 2016, 01:12:54 am
content: Exactly, I is for the intensity of the current.Side note: It's not only for ?, is the usual symbol for that variable in all the electric stuff. Usually in uppercase when referring to constant current (DC) and in lowercase for when it is changing. So much than the conventional imaginary number ?(-1) is expressed as j for most engineering and physics applications.JS

author: vulturebetrayer
author_rank: Contributor
timestamp: September 15, 2016, 01:16:40 am
content: Quote from: JS on September 15, 2016, 01:12:54 amIs the symbol supposed to be ? or is it a different symbol that the board DB screwed up?

author: vulturebetrayer
author_rank: Contributor
timestamp: September 15, 2016, 02:15:21 am
content: Quote from: evb149 on September 15, 2016, 01:20:26 amStrangely I don't have a problem with anode and cathode thanks to blowing up LEDs, and also I understand that current is actually backwards from how we design electronics. I have a lot to learn, and you guys are super helpful, so I appreciate any tips you have on studying these things.

author: rstofer
author_rank: Super Contributor
timestamp: September 15, 2016, 02:17:35 am
content: Quote from: evb149 on September 15, 2016, 01:20:26 amOr my personal favorites: curl and divergence

author: bitseeker
author_rank: Super Contributor
timestamp: September 15, 2016, 02:33:09 am
content: And, of course, volts may appear as V, E, or U.Hmm, there's power in you and I. (all puns intended)

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 15, 2016, 02:43:57 am
content: Hi,In addition the reasons stated above, C was already used for:C = Coulomb (unit of charge)c = Speed of light in a vacuumC for CapacitanceRegards,Jay_Diddy_B

author: vulturebetrayer
author_rank: Contributor
timestamp: September 15, 2016, 03:36:03 am
content: alright guess I'll get back to studying. . .

author: tggzzz
author_rank: Super Contributor
timestamp: September 15, 2016, 06:58:09 am
content: Ah, but wait until you start to consider "small signal" voltages and currents in non-linear components such as diodes and transistors etc. That's represented as "i", not "I".Wait until you start on the current flow through inductors and capacitors. That's at 90degrees to the voltage and is represented using complex numbers. Now a mathematician represents a complex number as "a+ib", which would be ambiguous where currents are involved - so "j" is used to represent sqrt(-1), as in "a+jb".

author: R005T3r
author_rank: Frequent Contributor
timestamp: September 15, 2016, 07:16:05 am
content: I use i for the imaginary unit, and yes I write i and I circle it.Maybe you should consider: s and 5 in the Fourier transforms, especially when you are at exams and you can't distinguish the variable to the bloody 5....

author: tggzzz
author_rank: Super Contributor
timestamp: September 15, 2016, 08:18:23 am
content: Quote from: R005T3r on September 15, 2016, 07:16:05 amDon't forget 2 and z. I've copied a maths lecturer, who scribbled furiously - and crossed his z.

author: R005T3r
author_rank: Frequent Contributor
timestamp: September 15, 2016, 08:35:21 am
content: Lectures at university = recording session.It's simply impossible to understand everything they say or take notes about whatever they do. The best way is to record everything(HD audio + video) they do and while you take notes you start adding up merkers in both the recordings and the notes. Guaranteed you can easly skip trought the lessions without wasting your time.Also, if you end up by taking notes in the wrong way, then when you want to study at home

author: tszaboo
author_rank: Super Contributor
timestamp: September 15, 2016, 09:07:22 am
content: The real fun starts, when you start learning Electro Magnetic Fields (or equivalent) and suddenly ? means five different stuff. I think we used up all the Latin and Greek alphabet twice over the course. Capital meaning different things.I still cannot write xi properly. Anyone wondering, it means Spatial frequency, Potential difference (AKA u), and something with Taylor.

author: tggzzz
author_rank: Super Contributor
timestamp: September 15, 2016, 09:19:43 am
content: Quote from: R005T3r on September 15, 2016, 08:35:21 amRubbish, unless at a rubbish university.The techinique I rapidly adopted was to scribble down everything they said/wrote, sort-of understanding it. Then, within half a day (while it was fresh in my mind), to go over my scribbles and re-write them (a) neatly, (b) comprehendably and (c) filling in the bits IthoughtI understood but then realised Ididn'tunderstand. That made the next lecture easier to follow, and made revision much easier.Sure, that's extra "unnecessary" work. Deal with it.HD video/audioand most handoutsare a trap, because it enables you to avoid (c) above. It is all too easy to convince yourself you understand something - until you try to "teach" yourself by explaining it to yourself.QuoteYes. See above for a good way of taking notes.

author: Dave
author_rank: Super Contributor
timestamp: September 15, 2016, 09:42:09 am
content: If students did all of that after every single day of lectures, who would have time for going out for beers?Checkmate.

author: tggzzz
author_rank: Super Contributor
timestamp: September 15, 2016, 11:43:40 am
content: Quote from: Dave on September 15, 2016, 09:42:09 am"After"is too late. I did it "during", within a couple of hours.That leaves adequate beer time!

author: Zero999
author_rank: Super Contributor
timestamp: September 15, 2016, 12:12:15 pm
content: Quote from: tggzzz on September 15, 2016, 09:19:43 amHas it ever occurred to you that different methods suit different people?I couldn't write fast enough to keep up with the lecturer. I used to take my laptop in any type a lot but that wasn't easy for formulae. I found it easier to focus on understanding it, rather than note taking. If I tried too hard to get everything down on paper, it would just be an illegible mess and I didn't take any of it in, so I might as well had not bothered going. Fortunately, I managed to get copies of the notes from the lecturer and other students.As long as you work through everything and make sure you fully understand it, it doesn't really matter whether you've physically written it down or not.Exams were a bit of a bugger but allowed a bit of extra time in exams to write everything down.What used to mess me up more than z & 2 was lower and upper case v for instantaneous and steady state voltage, even when typing it.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 15, 2016, 12:19:29 pm
content: I went to undidversity b4 lAptopz. The used overhead projectors.

author: helius
author_rank: Super Contributor
timestamp: September 15, 2016, 01:03:48 pm
content: Quote from: tggzzz on September 15, 2016, 06:58:09 amThat letter was already in use for sqrt(-1), but in a rather different context: Hamilton's quaternions, where there are threedifferentsquare roots of -1.\$ i^2 = j^2 = k^2 = ijk = -1 \$

author: R005T3r
author_rank: Frequent Contributor
timestamp: September 15, 2016, 01:23:08 pm
content: Quote from: tggzzz on September 15, 2016, 09:19:43 amI've already tried trust me, Actually, that was my method when I attended the college. In my university the mindset is: "who cares if you don't understand, the lecture must go on, and I must finish the day. The exams are made to f+ck you, so I can go in vacation earlier". With the method you said, you can't keep it up, it's simply impossible to do so: demonstrations are practically impossible to understand at first glance, not to mention that you will get distracted at some point and you will lose your concentration. At home you have to prepare the exams during the lectures (in some cases actually at the beginning of the lectures).You won't have half a day to spend on refining, rewriting or even understanding all the things. Rewriting neatly the things: It has proven many times to be a failure in so many subjects...I know that making videos and recording stuff is not the best way to understand everything, but at least you can have a track of the things you have done and if there's a mismatch from your notes you will soon realize what's wrong: I actually do myself the demonstrations(because if you follow the book you end up that 3 monts won't last). I see them as another tool to pass the exams, period. And I need to pass the bloody exams in order to get the degree, in ANY way.About social life? there's no social life, you have to study, hard and all the way trough, you stop more than 3 times? you will not pass your exam at this session. Also making friendships... All result in quite not durable ones and in some cases they will drop you because of the "competition climate" there is. Not to mention that companies promplty refuses anyone who have a degree that is not out from a prestigious university.

author: galvanix
author_rank: Contributor
timestamp: September 15, 2016, 01:52:37 pm
content: Quote from: rstofer on September 15, 2016, 02:17:35 amDon't forget about dots or x's because that's gonna change the operator, although it's always a drunk delta!

author: tggzzz
author_rank: Super Contributor
timestamp: September 15, 2016, 02:27:33 pm
content: Quote from: Hero999 on September 15, 2016, 12:12:15 pmStrawman observation; I stated what suited me and a potential disadvantages of other techniques. I did not state they were the only techniques.QuoteMy noteswerepretty illegible, andwereincomprehensible after a few hours. Hence my reiterating that it would be too late to wait until the evening.Using a laptop would have been impossible, not only for formulae but also for diagrams and annotations.QuoteI never trusted myself to remember it in 9 months time; the written notes were an excellent revision aid.

author: TimFox
author_rank: Super Contributor
timestamp: September 15, 2016, 06:57:32 pm
content: To be careful, remember that variables such asV(potential),C(capacitance), andc(velocity) are italicized, while units such as V (volts) and C (coulombs) are not italicized.

author: Zero999
author_rank: Super Contributor
timestamp: September 15, 2016, 08:00:59 pm
content: Quote from: tggzzz on September 15, 2016, 02:27:33 pmNonsense. Not every one is like you (thank goodness). People are different. Deal with it!Fair enough, you may learn very well by making written notes but don't expect everyone to be the same. Some people can learn very well from videos and books and there are some good distance learning courses where this is the sole form of study and written notes are no good if someone can't write because they have a disability.QuoteSpeed has always been my problem, more than readability. I can write very neatly for short periods of time but it takes ages and even if I write scruffily it's still less than half the speed of the average person. Imagine the lecturer is talking so fast you can't write it down quick enough, like if someone recorded it but play it back at double the speed and then try to take notes: that's what it was like for me.QuoteMy memory is excellent, as long as I'm interested in the subject and have a good understanding of it, I can remember it for a long period of time and if the course is just about memorising things, then it's very poor. Understanding and creative thinking is far more important than just memorising information, especially these days as it's very easy to access vast amounts of information.

author: Cerebus
author_rank: Super Contributor
timestamp: September 15, 2016, 11:35:48 pm
content: Quote from: tggzzz on September 15, 2016, 09:19:43 amWhen I was at university I developed a technique of helping friends and flatmates out when they were revising or had trouble with some area by getting them to explain things to me - essentially teach me what they'd learned. Then I'd ask awkward questions about the bits it seemed they didn't have 'quite right'. It worked well and I got them to do it to me too. From being on the 'explaining' end of it I can vouch for it being a good way to fix what you've learned into memory.I was studying computer science but walked away with an additional 1/2 a law degree, 1/2 a biochemistry degree, 1/4 a metallurgy degree and scattered corners of a maths degree. I probably learned faster from them than I would have if I'd actually been on their courses. The others walked away with part of a computer science degree. Weirdly, thinking about it, all but one of the aforementioned other students (the lawyer) is now working in computing.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 16, 2016, 12:28:20 am
content: It can make it difficult to hang on to the concepts, but don't get hung up on the symbols. There are various "schools" that developed independently from originators in different locations. Math people, engineering people, French people, German people, English people, Americans. Astronomers, physicists, chemists.It isn't just the symbols, it is the formulations. Take Fourier transforms for example. The basic idea is the same everywhere, but there needs to be a 1/(2*pi) normalization. Some authors put it in the time domain side, some put it in the frequency domain side and others split the difference and use sqrt(1/(2*pi)) in each domain.So the key is to know what is in use in each paper or resource you are using. The bad news is that it can be confusing, the good news is that if you can keep up, you really do understand what you are doing.