ohms law

[ericgibbs]

Yes, I've read and understood that but I've learned nothing new. It doesn't mean that Ohm's law doesn't apply at all V still equals IR, it's just that the resistance of a non-linear element just changes as a function of voltage or current as I explained a few posts ago.
https://www.electro-tech-online.com/threads/ohms-law.106871/#post875134

The part of the Wiki article discussimg Johnson–Nyquist noise doen't debunk Ohm's law any more than the random movement of particles in a liquid or gas above absolute zero violates the first and second laws of thermodynamics.

hi hero,
I am not trying debunk Ohms law, but the formula V= I * R is not Ohms Law.
Ohms Law defines the current flowing in a conductor is directly proportional to the applied voltage and inversely proportional to the conductors resistance.

You seem to have disregarded this section of the text:

In a true ohmic device, the same value of resistance will be calculated from R = V/I regardless of the value of the applied voltage V. That is, the ratio of V/I is constant, and when current is plotted as a function of voltage the curve is linear (a straight line). If voltage is forced to some value V, then that voltage V divided by measured current I will equal R. Or if the current is forced to some value I, then the measured voltage V divided by that current I is also R. Since the plot of I versus V is a straight line, then it is also true that for any set of two different voltages V1 and V2 applied across a given device of resistance R, producing currents I1 = V1/R and I2 = V2/R, that the ratio (V1-V2)/(I1-I2) is also a constant equal to R. The operator "delta" (Δ} is used to represent a difference in a quantity, so we can write ΔV = V1-V2 and ΔI = I1-I2. Summarizing, for any truly ohmic device having resistance R, V/I = ΔV/ΔI = R for any applied voltage or current or for the difference between any set of applied voltages or currents.

The point you are making regarding non ohmic is also valid, provided that the measurements are made over a short 'linear' section of say a diode curve.

 

[Hero999]

I am not trying debunk Ohms law, but the formula V= I * R is not Ohms Law.

EDIT:
What do you mean?

You seem to have disregarded this section of the text:

No, I read that section of text and concluded that V = IR whether the conductor is Ohmic or not, it's just that in non-linear loads R can vary depending on the current, voltage or temperature.

I think we're talking about semantics more than theories, as in the other thread.

The point you are making regarding non ohmic is also valid, provided that the measurements are made over a short 'linear' section of say a diode curve.

Yes, that's a very good way of looking at it.

 

[ericgibbs]

EDIT:
What do you mean?

hi,
Is this what you are asking.?

Ohm's law
(Physics / General Physics) the principle that the electric current passing through a conductor is directly proportional to the potential difference across it, provided that the temperature remains constant.
The constant of proportionality is the resistance of the conductor

When you ask most most people to state Ohms law, they quote the equation V=I*R, which is NOT Ohms Law, its only the equation for obtaining the values for a single point.

The important wording in Ohms Law is 'proportionality'
eg:

What is the definition of directly proportional?
A relationship where a number increases or decreases together with another number at the same ratio.
Directly proportional is the opposite of inversely proportional.
Mathematics. Having the same or a constant ratio.

Its not semantics, its the misquoting of Ohms Law that causes misunderstanding.

 

[Sceadwian]

Yeah Hero, Eric is trying to explain the same thing I'm trying to get across. If you don't want to read the entire thread then don't but take it as a matter of fact that it's true cause we've been down that road =) It's not often I so completely reverse my original opinion, which if you read my first posts is exactly the same as your current viewpoint, I spent about a week arguing with MrAl about it.

 

[Hero999]

I see your point, I'm not sure if I agree or not.

As far as I'm concerned Ohm's law is the formula but I'm not going to bother arguing because I don't think it's important.

 

[Sceadwian]

Well as long as you see the point think what you want, I'm not gonna try to brow beat it into you that's for sure! That thread was out of hand enough as it was, we don't need a second one =) I did eventually see what MrAl and eric were saying, but I'm still a bit on your side as far context goes, as the way you (and I did) think of it is so commonplace that more people think of it the 'wrong' way than the 'right' way so which way is really right? =)

 

[Hero999]

I'm not gonna try to brow beat it into you that's for sure! That thread was out of hand enough as it was, we don't need a second one =)

That's something I do agree on.

I think most people, including me often, don't know when to stop arguing.

 

[Sceadwian]

Well it's good that we're not arguing then =) God forbid either of us learn anything =\

 

[aquamon]

Pleaase!
Stop!
Thank you!
LoL!

 

[canadaelk]

Georg has been dead for more than 150 yeaers! Let him rest! E

 

[Sceadwian]

aquamon, that Ohm's law thread was put to rest ages ago, and everyone was happy at the end of it, or at least agreed to disagree on the fine details of it, you're the one that dredged it up, saying 'stop now' is more than a bit late =) I bet you're not laughing now at the validity of arguing about it though. Wars have been started on technicalities less subtle that this one I'm sure.

 

[aquamon]

aquamon, that Ohm's law thread was put to rest ages ago, and everyone was happy at the end of it, or at least agreed to disagree on the fine details of it, you're the one that dredged it up, saying 'stop now' is more than a bit late =) I bet you're not laughing now at the validity of arguing about it though. Wars have been started on technicalities less subtle that this one I'm sure.

'Cause I can't believe a simple electrical law would be argued in here, really?

I haven't even read the threads as I "learnt" in BASIC ELECTRICITY what it is in a DIRECT CURRENT circuit.

Later on in ELECTRONICS, I "learn't" about impedance and junctions...

Sheesh.

 

[ericgibbs]

'Cause I can't believe a simple electrical law would be argued in here, really?

I haven't even read the threads as I "learnt" in BASIC ELECTRICITY what it is in a DIRECT CURRENT circuit.

Later on in ELECTRONICS, I "learn't" about impedance and junctions...

Sheesh.

hi aquamon,
You should have been around when Dr Ohm first published his results, he was branded a heretic and worse.!! , no joke.

We are not arguing about his law, just discussing its different interpretations when used for modern semiconductor devices.

 

[Sceadwian]

aquamon, the more you learn the more you'll realize things aren't really as simple as you seem to think, that is one of the reasons electronics is so intimidating to many people. They're bits you have to plug into each other that owe their functional existence to effects that only exist on an atomic scale.

You may have heard of something called a tunnel (Esaki) diode, they have characteristics that are useful for a few various reasons, mainly in microwave oscillators and hyperfast rectifiers. Their negative resistance region functions via quantum tunneling which on a macro scale would be akin to solid matter phasing through other solid matter if it were moving at just the right speed, the effect only works on the subatomic scales though.

 

[aquamon]

aquamon, the more you learn the more you'll realize things aren't really as simple as you seem to think, that is one of the reasons electronics is so intimidating to many people. They're bits you have to plug into each other that owe their functional existence to effects that only exist on an atomic scale.

You may have heard of something called a tunnel (Esaki) diode, they have characteristics that are useful for a few various reasons, mainly in microwave oscillators and hyperfast rectifiers. Their negative resistance region functions via quantum tunneling which on a macro scale would be akin to solid matter phasing through other solid matter if it were moving at just the right speed, the effect only works on the subatomic scales though.

As you are so knowledgeable, please go figure out how to reset this.

This is what I'll do to manufacturers that don't assist when contacted:- REVERSE THEIR DAMNED CRAP!

That's all that I'm really interested in right now.

Thank you.

 

[Mikebits]

Well since you asked so nicely, I think to clear the faults, you use the remote pin.
According to data sheet.

When the system has latched (either after overcurrent
or overvoltage condition), the system
needs to be reset via the Remote input.

But if whatever caused the fault condition still persist, then it will most likely return to the faulted state.

 

[aquamon]

Well since you asked so nicely, I think to clear the faults, you use the remote pin.
According to data sheet.
But if whatever caused the fault condition still persist, then it will most likely return to the faulted state.

Moved here