short me out - Page 1
Forum section: electronics / beginners

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 06, 2014, 01:23:13 am
content: this is for a school project BTW and will probaly post on this thread for more help with it some questions will be longer than others. couldn't find an answer anywhere else but is it true that nothing can be a pure short circuit since nothing is a perfect conductor and there will always be resistance so it will always be a "circuit".

author: c4757p
author_rank: Super Contributor
timestamp: May 06, 2014, 01:28:19 am
content: Quote from: noah_fakelastnamelike_bob on May 06, 2014, 01:23:13 amYes, for the most part. If you want to be obsessively correct, superconductors have literally zero resistance, but those won't exist in a practical circuit (and even still, the point where you connect to them would have some resistance, I'd think). No matter how good the conductor, it will havesomeresistance.A point, though - it's still a "true" short circuit, as the word "short" just implies exactly that: your circuit was supposed to complete a long path, but you accidentally made it short - directly out of the battery and back around, rather than through a lamp, for instance.

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 06, 2014, 01:31:11 am
content: thank you + my ocd will cost me thousands in superconductors lol jk.

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 06, 2014, 02:13:31 am
content: is this correct or do i have it the opposite way around for redoxthis is directly from my power pointRE=REDUCTIONOX= OXIDATIONTO ME THIS DOSENT MAKE SNESE TO ME BUT WHAT EVER…WHEN it does the “RE” thing it will gain electronsWhen it does the “OX” thing guess what it loses electrons

author: Legit-Design
author_rank: Frequent Contributor
timestamp: May 06, 2014, 03:14:47 am
content: Quote from: noah_fakelastnamelike_bob on May 06, 2014, 01:23:13 amhttps://en.wikipedia.org/wiki/Order_of_magnitudeDave did put it really nicely in one of his videos. Went something like this "when something is an order of magnitude out of what are you trying to do, you don't generally need to worry about it". I think it was something related to ucurrent and error calculations. But same still applies.You will know when you are pushing high currents through pcb tracks or conductors. A car starter might take 100 amps from a battery in normal cars, and several hundred amps on american cars. So you need fat cables and low resistance. You can have more resistance and more heat in the cables or less resistance and less heat in the cables, but cables will still heat up. All depends how much you want them to heat up and how much they can safely heat up, add some safety margins to make sure.Quote from: noah_fakelastnamelike_bob on May 06, 2014, 02:13:31 amYou only have the power points and no teacher actually explaining it? In that case, good luck. Anyways that sounds more like Chemistry to me.http://www.chemguide.co.uk/inorganic/redox/definitions.html

author: PedroDaGr8
author_rank: Super Contributor
timestamp: May 06, 2014, 03:36:30 am
content: I learned LEO GER (pronounced like grr of a tiger)Loss of Electrons, oxidation. Gain elections, reduction

author: Kremmen
author_rank: Super Contributor
timestamp: May 06, 2014, 04:53:17 am
content: Quote from: noah_fakelastnamelike_bob on May 06, 2014, 01:23:13 amActually, something can (be a pure short circuit). Back in the day the Tech Uni of Helsinki and Stromberg, a pioneering power electronics company, now part of ABB made a superconducting test motor and ran it in the cold lab in the Uni campus (same facility by the way where several world records of low temp were achieved). I was acquainted with the motor so i can state that there actually is (or was) such a thing as a perfect short. This is how it was done:The motor in question was a unipolar DC machine which is not important as such. The point is that a feature of the mechanical construction was a coil in the center of the machine, providing the (radial) magnetic field against which the rotor torque was developed. This coil was contained in a supercooled barrel and during operation the field current (a few hundered amps) circulated indefinitely without an external supply. So in that sense it was a perfect short.Initially the current was supplied from a conventional source. The clever part was that the terminals of the source were were shorted with a piece of superconducting wire contained in the same barrel as the rest of the coil. Only this piece was slightly heated to keep it out of superconduction. The result was that none of the current flowed through this wire as these was a parallel superconducting path through the actual coil. Once the current was established, the heating was stopped and when the short became superconducting you just disconnected the supply and Bob was your uncle.Pure short, perfect conductor. Current circulates forever without an external supply.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 06, 2014, 05:17:54 am
content: Yes, superconductors can and do work, and they really have zero resistance. What kremmen described (with the thermal switch) is indeed the standard way that superconducting magnets are made, and MRI machines in hospitals all over the world now use this technique to run for years, as do the magnets that steer particle beams in the LHC (although those magnets get ramped up and down deliberately as part of the acceleration process). Of course from that observation you can only say that the resistance is fantastically small, but it turns out to actually be zero resistance.The need for liquid nitrogen or liquid helium cooling puts a bit of a damper on all but a few applications.

author: electronics man
author_rank: Frequent Contributor
timestamp: May 06, 2014, 01:08:24 pm
content: a short circuit is relative if you want a resistance of 1Mohm and the true resistance is 10ohm it's a short, if you have a heater with a resistance of 2ohms then that is not a short. All a short circuit is is an undesired low resistance.If a power supply is damaged by a short depends on the resistance of the short, the maximum current output of the power supply, if you have a 1ohm short across a 5V 30A power supply you won't damage it, you will just destroy you wires or trace, if it is across a 5v 1A power supply you may damage it.

author: Rudane
author_rank: Regular Contributor
timestamp: May 06, 2014, 04:00:37 pm
content: Google negative resistance. That's my best answer...

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 30, 2014, 03:19:44 am
content: can some one reveiw it for me please

author: TimNJ
author_rank: Super Contributor
timestamp: May 30, 2014, 03:27:26 am
content: I'm not sure where you are in your education or what the context of the project is but it seems a little "unprofessional" (?). As in, you use some "slang" etc. If that's appropriate for the class then go for it. But if I were you I'd probably just try to make everything neat and with proper grammar.

author: IanB
author_rank: Super Contributor
timestamp: May 30, 2014, 04:10:43 am
content: Quote from: noah_fakelastnamelike_bob on May 06, 2014, 02:13:31 amTo understand this, go back to your chemistry.Oxidation and reduction occur together. If two molecules A and B react together, then if A is oxidized B is reduced, or if A is reduced then B is oxidized. Hence "redox": reduction/oxidation.Now a common oxidizing agent is oxygen (who would have guessed?), and oxygen has a lack of electrons in its outer shell. So when it reacts it wants to grab more electrons to fill the space. If oxygen is oxidizing something, it is stealing electrons. Therefore the thing being oxidized is losing electrons to the oxygen.On the other hand, a common reducing agent is hydrogen. Hydrogen has a spare electron floating around without a partner. So when hydrogen reduces something, it gives away its electron to the other reacting molecule to make things tidy. So the thing being reduced is being given an electron by the hydrogen.We can see this when hydrogen and oxygen react together to form water. The hydrogen is oxidized, the oxygen is reduced, and the two parties are so happy to make this exchange that the whole thing goes off with a bang.

author: hamster_nz
author_rank: Super Contributor
timestamp: May 30, 2014, 04:40:49 am
content: My favorite Redox reaction has to be thermite (Iron Oxide and aluminum powders). Well worth searching for on youtube.I am not sure if they would teach that in school anymore...

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 30, 2014, 05:17:47 pm
content: Quote from: TimNJ on May 30, 2014, 03:27:26 amthis is intended to be normally taught to high schoolers ( 9th- i think 12 graders)while i am teaching it to be in a loses environment and it is intended to have a unprofessional feeling.i had also ran across this guy on YouTube and he explains everything PERFECTLY to mehow to teach ohms lawwhat is volts ohms and ampshow can i go about being able to teach this in a class room because to use his videos or anyone's for that matter don't i have to get permission by some dumb law? i live in America Missouri

author: IanB
author_rank: Super Contributor
timestamp: May 30, 2014, 06:39:01 pm
content: What exactly is the scenario here?You are a high school student doing a classroom project where you prepare a presentation demonstrating your understanding of the material?Your presentation is to be made as if you would be teaching it to other students?Echoing the comments of others you should be more formal in your presentation style and avoid silliness.Concerning your question about YouTube videos: you watch the videos for inspiration, and then you prepare equivalent material yourself for live presentation. Showing other people's videos is lazy and is not of any benefit to your own education.(Also, why do you say "electricity flows from negative to positive"? Saying that will just confuse people, since the whole point of positive and negative is that current flows from positive to negative. Don't confuse your audience, follow the accepted convention.)

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 31, 2014, 08:25:48 pm
content: the scenario is that my school currently only teaches series and parallel, ground and other very basic thing's. it is not very encouraging for some of the students who have actually studied electronics before at all. i have offered to make more in depth course for students. this is not a graded thing at all its is to teach future students about electronics. i am a freshmen, but this is being taught to 8th graders. most likely when the teacher presents it to the students i will most likely not be able to be there and help so i would rather have videos to help the teacher. using silliness is a way to make students more comfortable when they are being presented, since i am told this so much i am going to take it off.i am going to have to make some real circuits i was presented with a bag. it has a bread board. a bunch of resistors with different values a crap ton of transistors 2n 3906/3904, and s106b1a bunch of caps ceramic and electrolytic . and also a bunch of diodes. and some you guessed it 555 timer chips. so yea any things other than the obvious flashers help find a bunch of simple circuits would help.

author: TimNJ
author_rank: Super Contributor
timestamp: May 31, 2014, 08:53:11 pm
content: Okay, I don't think a small joke here or there is a bad thing, but there's a reason that textbooks and technical books aren't written in the way you did in your pdf. While comic relief is good, the comedic part can get in the way of good learning. Not saying you should be boring and plain, but just find a better balance.Best of luck.

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: May 31, 2014, 08:57:15 pm
content: yea i will probably delete most of it but then keeps some show to my teacher and the discuss more about it

author: noah_fakelastnamelike_bob
author_rank: Regular Contributor
timestamp: June 05, 2014, 03:31:06 am
content: here is the nextupdate on the power point.rev. 0.02 i guess thanks for any help along the way. Mrs. long click the link below this post and it should download the pdf for you

author: corrado33
author_rank: Frequent Contributor
timestamp: June 05, 2014, 05:01:07 am
content: Presentations are always MUCH better when the presenter uses proper English on their slides. Remember that. From the thread I'm guessing you're in high school. If you try to make a presentation about electronics funny, you'll regret it later. (Because it will inevitably not be funny.) Especially if you're not presenting it!Stick with one color scheme. Don't jump back and forth. Don't do red text on a black background, it's hard to read and hard on the eyes when the previous slide was white. Be consistent with text font/size/color. The key is consistency, in everything. Use DESCRIPTIVE headings to slides. A person should be able to read the title of the slide and know the gist of what the slide is about without seeing the rest of the slide. Use sentences.

author: TimNJ
author_rank: Super Contributor
timestamp: June 06, 2014, 04:49:12 am
content: Hmmm...I feel that you're not quite getting the point. I understand you want to be entertaining, but it's it's almost assuredly better to present material in a way that is consistent and not confusing, which your presentation is a little. Don't write so many "well"s and "alright"s.Your slide is there for information, not to do the talking. The teacher (or you) are talking when the lesson is taught, so therefore there is no need for the slides to be "talking at the class".I linked to the download of one of the presentations I did for high school electronics class.http://ge.tt/1mlA2TE1/v/0?c