Ohm's law in not an approximation. It describes the exact relationship for voltage, current and resisitance and is summed by the V=IR equation, just like the famous E=MC^2 relationsip sums up another famous law. Ohm's law is true for all materials, although the law is not material dependent.
Show me a material that doesn't exhibit continuity.proportionality refers to a continuous function
Ohms Law
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16th June 2009 10:05 PM #51giftiger_wunsch
By saying that two variables are directly proportional, it is saying that the two variables have a positive, linear relationship. Just as Hooke's Law approximates that the extension of a material is directly proportional to the force applied to it, which is not true for non-hookean materials, Ohm's law approximates that voltage is directly proportional to resistance, which is not true for non-ohmic components.
V = IR and variants are used to calculate V, I, or R from a single set of data; proportionality refers to a continuous function.
What is really being stated is that V(x) = IR(x) for a point x. This implies that current, I, is a constant, which we know is not necessarily the case.0Last edited by giftiger_wunsch; 16th June 2009 at 10:13 PM.
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16th June 2009 10:11 PM #52BrownOut
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16th June 2009 10:44 PM #53BrownOut
Look Georg Simon Ohm: The Discovery of Ohm's Law
And Here:The relation V / I = R even holds also for non-ohmic devices, but then the resistance R depends on V and is no longer a constant
Georg Ohm
I guess if you want to go around denying the laws of physics, then nobody can stop you. [ET: REMOVED SENTENCE]The equation I = V/R is known as "Ohm’s Law".0Last edited by The Moderation Team; 17th June 2009 at 01:51 AM. Reason: Insulting other members
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16th June 2009 10:48 PM #54giftiger_wunsch
Clearly we're not going to come to an agreement, so I'm just going to leave it at that.
[ET: REMOVED SENTENCE]0Last edited by The Moderation Team; 17th June 2009 at 01:52 AM. Reason: Removed retaliation.
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16th June 2009 10:55 PM #55BrownOut
[et: Removed sentence]
0Last edited by The Moderation Team; 17th June 2009 at 01:55 AM. Reason: Removed insult and infraction given.
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16th June 2009 11:22 PM #56timsvb
Been havin a look at your discussion.I'm a newbie too.Have a look at this site.
Ohm's law calculation calculator calculate magic triangle equation tip online voltage volts resitor resistance amps amperes audio engineering - sengpielaudio Sengpiel Berlin Seems you are both right,but pretty tight fitting to your ideas.S'pose the key word is "Non-Ohmic" components.Looks like others have sorted this out before.They have defined deals as non compliant with a very sound law.Ohms law is a very powerful tool,and if we forget our laws and "Rules of Thumb",we also dispense with our first port of call as far as any diagnostics are concerned.My two cents.0
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16th June 2009 11:41 PM #57BrownOut
That's a mis-statement. Ohm's law holds for non-ohmic materials. I refer you again to this: Georg Simon Ohm: The Discovery of Ohm's Law
This is important. Later in your technical career, you'll have to understand concepts like Small-Signal Resistance. That concept demands that ohm's law holds even for non-linerar resistance materials, aka so called non-ohmic.0Last edited by BrownOut; 16th June 2009 at 11:42 PM.
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17th June 2009 12:07 AM #58timsvb
This is from your link above."As stated above, this work included “Ohm’s Law” theory: The relationship of a current passing through most materials is directly proportional to the potential difference applied across the material."
Not out for a stouche, but have an open mind.Don't know whether "most" refers to what you guys were talkin about but "most" doesn't include everything.I'll keep it in mind as I further my career, and leave well enough alone for now. Thanks for the tip.
Regards tim from oz.0
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17th June 2009 12:11 AM #59BrownOut
As I already said; that's a mis-statement. Ohm's law works for all materials. The law relates physical quantities, and is not dependent on material.
The author made a nice calculator applet, but he doesn't really understand the law.0Last edited by BrownOut; 17th June 2009 at 12:11 AM.
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17th June 2009 12:15 AM #60timsvb
me either.Just as well only lost two cents.
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