# Talk:Electrical resistance and conductance

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## various things to divide up right now

We are going to discuss this page. This page is about what electrical resistance is. Electrical rsistance is measured in ohms. The way it explains is very complicated. Electrical resistance is the flow of electricity or the current of electricity.

Something is wrong with that last sentence above. On the article, the term negative resistance doesn't seem right to me. A negative resistance would flip the current or voltage (but not both). Does the author mean negative resistivity with respect to some other value, such as temperature? Rich

What's this ? Someone wrote Ohm's law-but, it's only for DC, not AC where you got sine and other things. Look at some basic physics (or electromagnetism, or electrical engineering) textbook, for Chrissake.Mir Harven 16:10, 13 Apr 2004 (UTC)
ohms law works for a resistor whether the cuircuit is DC or AC. It can also be used with inductors or capacitors by using phasors and impedences represented by complex numbers. Neither of theese requires use of sine and cosine Plugwash 14:07, 8 Dec 2004 (UTC)
What was wrong with the version from 22:56, 3 Dec 2004? The most recent edit even omits the mention of ground, or even a reference point, without which the concept of resistance is hard to understand or measure.Ancheta Wis 18:14, 8 Dec 2004 (UTC)
measuring with respect to an arbitary reference point seems far mroeo confusing to me than just stating the voltage accross the resistor. I have NEVER seen a book that uses votlages relative to an arbiary reference point in its basic description of the rule

My mental model is

• A - a voltmeter with a red lead and a black lead.
1. touch the black lead to point 0, say ground
2. touch the red lead to point 1, say the bottom of the resistor (closest to ground)
3. V1 = the reading from the voltmeter.
4. touch the red lead to point 2, say the top of the resistor. but keep the black lead at the same point 0. It is the reference point.
5. V2 = the reading from the voltmeter.
6. V2-V1=voltage across the resistor.
• B - Now get a current meter, and measure the current draw.
1. I = the reading from the current meter
2. R=(V2-V1)/I

If the books don't say this, you need better books. And you might hurt yourself if you don't know the basics and you can't even measure the voltage and current. Be careful during the measurement. Try to use one hand if possible, and an alligator clip to the reference point. Ancheta Wis 00:56, 9 Dec 2004 (UTC)

I wrote this without knowledge of how you chose your user-name; it is ironic that you should choose this topic to edit. Take care. Based on the evidence, I am reverting to 22:56, 3 Dec 2004. Ancheta Wis 10:55, 9 Dec 2004 (UTC) P.S. it looks like some references to electrical safety and natural hazards are in order for this article and the related set of topics.
ahh the source of my username...long time ago...i was much younger and less ensible then
i can see what you are getting at but isn't it far simpler to just measure the voltage accross the resistor directly (that is red lead to one end blkack load to the other read off the voltage (V) accross the resitor directly then R=V/I)? not to mention more accurate as well (especially in an AC system or if the value of the resistor is small) I can see uses of your method if you are trying to figure out a lot of things about a cuircuit or possiblly if you are workign on dangerous voltages and therefore are working one handed but for the initial introduction of the formulae it is just overcomplicating things. Plugwash 11:58, 9 Dec 2004 (UTC)

The better books describe it simple first. Add my vote that it's counterintuitive and confusing to begin the explanation of a simple voltage drop with its definition as the difference between two differences between two points and a completely arbitrary and irrelevant third reference. The potential across the component is a single dimension, and it should be given as such. It would be perfectly fine to include the difference formula as an additional way of explaining it though.

I also don't consider it necessary to elaborate on practical issues in any article whose main topic should be the abstract definition of a physical property. Concrete safety-related issues about measuring instruments and their use aren't specific to resistance. A simple link on electrical safety in the 'see also' section should suffice, if any. Femto 14:43, 9 Dec 2004 (UTC)

Is there any reason why http://en.wikipedia.org/wiki/Electronic_color_code is not mentioned in this article?

added links in the caption to the resistor image --Ancheta Wis 08:54, 3 May 2006 (UTC)

## Resistivity and Salt Water

The article says resistivity varies "greatly" with salt concentration. Would anyone care to quantify that? There is math there and I think worth while mentioning ionic v. covalent bonding and how salt and dirt change the bonding properties of water. How about a source? Anyway I was just looking for the actual formula and dissapointed not to find anything. Wiredrabbit (talk) 18:47, 9 December 2008 (UTC)

## Question

My father wants to know what resistance have 5ppm of silver ions in water. He needs the number and the formula. Does anyone know how to calculate this? Thanks. --Eleassar777 17:03, 1 Jun 2005 (UTC)

## Measuring resistance

I think that by definition, measurement of the resistance of a conductor would assume that the proper terminations had been made from the measuring device (ohm meter, mutimeter etc) to the resistance under measurement. I therefore think that the statement about c'ompletly covering the ends' is superfluous.

Does anyone agree or disagee??Light current 20:34, 1 August 2005 (UTC)

What do you define as 'Scattering events' in a wire? -Grim- 10:40, 27 March 2007 (UTC)