Both R and V are variables. There isn't anything special about V that gives it some special status over R. In any real cirucit, you can vary V AND R to affect the current, which is also a variable. Constants are things like the Universal Gravitation Constant, Avogrado's Number and Boltzmann Constant, as in the previously mentioned, PV=nRT. In the case of Ohm's law, the constant of proportionality is unity.
If R was a constant, they it wouldn't be included on the little triangle that noobs use to calculate these quantities. Do you ever see anyone calculating Boltzmann's constant from pressure and temperature?
A, B, C and D are irrelevant.
shimniok:
Then i guess you should argue with the writers of those definitions because they all say proportionality exists in the Ohm's Law. R is a CONSTANT.
I think you're getting off-track with your irrelevant questioning. I've given you 3 good examples of constants, so why continue to pursue this? In all of the equations we've discussed, we can easily define the constants and variables:
F = Gm1m1/R^2; G is constant m1, m2, and r are variables
PV = nRT; R is constant, P, V, n, and T are variables.
E = IR; E, I and R are variables.
See? I can tell a constant from a variable.
But I'll answer your question. A, B, C and D are simply coefficients. They can be constants, vaiables or functions. If you don't believe me, look at the insert. These lines are described by the equation: (rearranged to look like your equation)
-1/2uCoxW/LVds^2 + 1/2uCoxW/L(Vgs-Vth)Vds - id = 0
Notice how the first order coefficient is allow to change? If it were strictly a constant, that would not be allowed.
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In my application i need to use the equation:
y=A*x^3+B*x^2+C*x+D
where
A, B, C and D are predetermined constants.
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You're wasting space and time with trival questions. I've already answered your question, and coefficients are, in genreal, not constants.
If you have any non-trivial questions, I'll answer. Otherwise, we're done here.
You have defined them as constants, so they are constants, obviously.
Are you saying that A, B, C, and D MUST ALWAYS be constants in that equation whether or not you explicitly define them as constants?
Here's another example:
In my application I have a thermistor attached across an ideal voltage source of fixed value (9V). The resistance of the thermistor is (heheh) proportional to temperature given by the function, say, Fr(t) = 2t
In the case of this particular circuit:
V = IR
where V=9V, R=Fr(t)=2tΩ
Is R a constant, coefficient or variable? Why?
Is V a constant, coefficient or variable? Why?
What about I?
Michael
Hi,
That's your opinion. Even when it is predetermined that A,B,C,D are
constants ahead of time for a given application you can not admit
that they are constants. That was my point. Once you get past
that, we can move on.
so many web sites
so many professors all state R as a constant
Yeah, all those websited are written by physicits. NOT!
You'll only find Commumity College professors making claims so clearly wrong. You'll never hear a claim like that in advanced physics lectures.
I think what is happening is that just because resistance is measured
in 'ohms' they think all resistance is somehow defined by Ohm's Law.
Ohm's Law is a very specific relationship between v and i, and without
R being constant there is no relationship to speak of.
...
The key to understanding this is in the phrase "in direct proportion to",
that's why i started this thread talking about that unique relationship.
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