Ohms Law Right Again - Silicon Wire One Atom Tall, Four Atoms Wide  - Page 1
Forum section: electronics / general

author: SgtRock
author_rank: Unknown
timestamp: January 07, 2012, 02:51:02 am
content: Greetings EEVBees:--See the below link for the Science Daily write-up of an article from Jan. 2012 Science, about how a team of researchers from the University of New South Wales, Melbourne University and Purdue University have created a Silicon wire, one atom tall, and four atoms wide. Measurement confirms that Ohms Law applies and is accurate even at the smallest scale.http://www.sciencedaily.com/releases/2012/01/120105161826.htm--This probably comes as no surprise to many of you EEVBees. I only bring this up because of some of the questionable assertions made about Ohms Law in this very forum. Various posters (who shall remain nameless) have said things like (I paraphrase): "Ohms Law is not really a Law, it is just something humans made up", and "Beings out in the Universe will have never heard of Ohms Law", and "In physical practice Ohms Law never works exactly", and various other Sophomoric quibblings.Ohms Law seems to apply even at the most massive scale; Please see the below link for an excerpt from an article in the Journal of the American Physical Society wherein the authors assert that Black Hole electrical activity satisfies Ohms Law.http://prd.aps.org/abstract/PRD/v18/i10/p3598_1--If any of you have a subscription to Science, or the Journal of the American Physical Society and can see behind their Pay Walls, please feel free to comment."The language of experiment is more authoritative than any reasoning: facts can destroy our ratiocination—not vice versa."Alessandro Volta 1745 1827Best RegardsClear Ether

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 20, 2012, 09:00:09 pm
content: ohm's law is a beautiful mathematical piece of art..aye

author: slateraptor
author_rank: Frequent Contributor
timestamp: January 21, 2012, 11:49:22 am
content: Apparently, someone (who shall remain nameless) has never studied diodes, transistors, or any other non-linear device.

author: tinhead
author_rank: Super Contributor
timestamp: January 21, 2012, 01:37:41 pm
content: Quote from: SgtRock on January 07, 2012, 02:51:02 amafaik this observation has been not confirmed later

author: olsenn
author_rank: Frequent Contributor
timestamp: January 21, 2012, 01:52:23 pm
content: I still stand by the fact that Ohm's law is NOT a natural law... it is a convenient system for communicating to other engineers. It should be no surprise to anyone that if we define "V=IR" than in every experiment "I" turns out to be "V/R".One thing I will say about that experiment though is that it's nice to see someone managed to make a wire that small. I hope P=IV is kept small because I can't imagine it will hold up under much stress

author: slateraptor
author_rank: Frequent Contributor
timestamp: January 21, 2012, 02:09:51 pm
content: Quote from: olsenn on January 21, 2012, 01:52:23 pmIt's a natural "law" in that it's an expression that analytically approximates observed empirical data under controlled experimental conditions. Diodes don't obey OL. Transistors don't obey OL. Any non-linear circuit element for that matter doesn't obey OL. I feel like so often people forgot (more likely completely unaware) that these so-called "laws" are nothing more than abstractions that make certain assumptions about what factors can be neglected and thus completely ignored.

author: olsenn
author_rank: Frequent Contributor
timestamp: January 21, 2012, 02:18:08 pm
content: Exactly right, slateraptor!

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 21, 2012, 02:44:44 pm
content: Quote from: tinhead on January 21, 2012, 01:37:41 pmwas it mr ohm himself ? because he didn,t have to worry about voltage drop over semi-conductors coz they hadn't been invented then ..meh

author: G7PSK
author_rank: Super Contributor
timestamp: January 21, 2012, 04:10:54 pm
content: Ohms law works on semiconductors that's why they get hot, (I2R losses)

author: slateraptor
author_rank: Frequent Contributor
timestamp: January 21, 2012, 04:18:29 pm
content: Quote from: G7PSK on January 21, 2012, 04:10:54 pmHow certain are you that it's indeed I2R losses and not V2/R losses?

author: firewalker
author_rank: Super Contributor
timestamp: January 21, 2012, 04:28:17 pm
content: Ohm's law is like Newton's law. The problem is in the word used?Alexander.

author: G7PSK
author_rank: Super Contributor
timestamp: January 21, 2012, 04:57:51 pm
content: Whats watt

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 21, 2012, 05:08:35 pm
content: what about a tunnel diode negative resistance stuff quantimised mechatronics..meh

author: G7PSK
author_rank: Super Contributor
timestamp: January 21, 2012, 05:46:06 pm
content: when you get into the field of quantum mechanics you cannot be sure if that which you would like to measure is actually there or elsewhere if at instant of measurement it is elsewhere its not measured or is it?

author: Rufus
author_rank: Super Contributor
timestamp: January 21, 2012, 06:40:11 pm
content: What a dumb thread and dumb law to try to pick holes in.Ohm's law is always right because it is only applicable to ohmic conductors the definition of an ohmic conductor being one that obeys ohm's law.

author: SgtRock
author_rank: Unknown
timestamp: January 21, 2012, 08:29:50 pm
content: Greetings EEVBees:--Egads they are coming out of the woodwork. "Ohms law is not a Natural Law." Feh! And what pray tell is a Natural Law. Ohms Law is one of the Laws of Physics. You will note that in Physics text books there is no footnote saying that Ohms Law is not a Natural Law. As a matter of fact I am unaware of any footnote mentioning any law not being a natural law.--"Diodes do not obey Ohms Law". Arrgh. Wrong! I suppose balloons do not obey the Law of Gravity. After all they do not fall with an acceleration of approximately 32 feet per second per second.--If any of these sophomoric contentions had merit, you would see them on the cover of prominent scientific journals."I could see that, if not actually disgruntled, he was far from being gruntled."P. G. Wodehouse 1881 1975Best RegardsClear Ether

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 21, 2012, 08:41:17 pm
content: have a word with Leo Esaki about the diodes...meh

author: Excavatoree
author_rank: Frequent Contributor
timestamp: January 21, 2012, 08:57:06 pm
content: What if we consider that resistance is not always a constant? Could even the semiconductor Current vs Voltage equations be written in the form I=E/R if we defined R correctly, and as a function of E, Temperature, and other factors? Why must we say "well, Ohms law doesn't apply to this device or that," when we could, perhaps, mean simply that for a particular device, R is not a constant and this Ohms law is no longer a quick, convenient equation to solve?In other words we might not have to "throw Ohms law away" or cast dispersions because "it doesn't hold for this or that device."

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 21, 2012, 09:01:45 pm
content: what about the negative resistance bit ? .thats freaky

author: Unknown
author_rank: Unknown
timestamp: January 21, 2012, 10:17:18 pm
content: From scanning through theScience article, my impression is that with their main claim is that their conductors, which are only a few nanometer wide, have a constant resistivity, i.e. resistance decreases linearly with the electronic cross section of the conductor. Previous attempts at creating tiny conductors would have a very sharp increase in resistivity once the diameter dropped below 100 nm or so. See figure 2C if you have access to the article. So their application of Ohm's law is about the current density as a function of the electric field, not about the relation between voltage and current. Their voltage appears to be a constant 500 µV.Quote from: B. Weber et al. 2012

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 21, 2012, 10:28:01 pm
content: alm.got no access .print screen it for us all and post.i'd like to see that