Talk:Current divider

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Can someone change the current divider law picture. The law is Rx_current_unknown = Itotal_x(R_total/Rx) the picture has an extra R total at the bottom of the denominator —Preceding unsigned comment added by 99.249.120.189 (talk) 20:12, 9 January 2011 (UTC)

I am not shure what needs to be cleaned up in it. i agree that some pictures would help but since i cannot host any..

as for merging it with the resistors i would have to disagree. It does not mention how to find current through a resistor.

A merge to Ohm's Law would seem more appropriate. Note that merge means summarise in the other article, not just redirect. - Just zis  Guy, you know? ^[T]/_[C] AfD? 22:12, 11 December 2005 (UTC)

Ohm's law talkes about how voltage equals current divided times resistance

Gee, really? And how do you think the current divider (and potential divider come to that) equations are derived? Please note: I do have some minor understanding of this, my (B.Eng) degree is in electrical engineering and I learned Ohm's law on my father's knee, since he was an electrical engineering teacher at a college :-) I'd say that at the very least Voltage divider and Current divider should be merged and actually I'd put both in Ohm's law since the three articles are inextricably linked. - Just zis  Guy, you know? ^[T]/_[C] AfD? 09:58, 12 December 2005 (UTC)

Somebody add a proof please? i had to figure it out on my own — Preceding unsigned comment added by 94.209.183.26 (talk) 16:31, 18 September 2014 (UTC)

The rules

It is true that the CDR and VDR and Ohms law are the very basics of electrical enginering. however i disagree with you comments that they should be merged into the ohms law.

Current Divider and Voltage Divider do use ohms law and are a pratical application of it. however they are seperate elements and most textbooks i read have them divided up into different sections as well. 08:19, 17 December 2005 (UTC)

Alternative Method?

There seems to be another way of using the current divider rule. The formula is slightly different. I suggest adding this to the article as well if this method is correct. Here's the link to the site: http://www.wisc-online.com/objects/index_tj.asp?objID=DCE3502 --Pavithran 08:50, 4 October 2007 (UTC)

Nope, it looks the same. Only difference might be that they define R_T = R₁ + R₂. -Roger (talk) 18:05, 6 January 2008 (UTC)

While the answer is the same, I think that the algebraic idea of using R_T = (the total resistance of the "parallel network") pedagogically makes more sense for people learning how to solve circuits. If we use a property of parallel circuits, that the voltage across each component is the same: V_T = V₁, and then apply Ohm's law for finding voltage from resistance and current, then I_T*R_T = I₁*R₁. From this stage, solving for the current is significantly more simple, I₁ = R_T/R₁*I_T . This solution was inspired by my Circuits I professor's lecture. ~(Can't sign for security reasons, the IP Address is at Rochester Institute of Technology). — Preceding unsigned comment added by 129.21.69.191 (talk) 17:53, 12 October 2022 (UTC)

Article should be renamed for consistency

Since current division is the dual of voltage division, I propose we rename this article for consistency. Plus I don't think I've ever heard the term "current divider rule". People usually just say "current divider". -Roger (talk) 17:01, 6 January 2008 (UTC)

I agree that the added word "rule" for both current and voltage cases departs from standard usage. It should be dropped in both cases. Brews ohare (talk) 17:39, 6 January 2008 (UTC)

In addition, the voltage divider article is more complete and should be made a model for this page as well.Brews ohare (talk) 17:43, 6 January 2008 (UTC)

I have rewritten the intro, made some corrections, and redirected this page to avoid the term rule. Brews ohare (talk) 18:56, 18 January 2008 (UTC)

Is there an error in the resistive divider paragraph?

According to my book the right way to find $I_{x}$ is $I_{x}={\frac {R_{T}}{R_{x}}}I_{T}$ where $R_{T}=R_{1}\parallel R_{2}\parallel R_{3}\parallel \ldots \parallel R_{n}$. If we use the formula $I_{x}={\frac {R_{T}}{R_{x}+R_{T}}}I_{T}$ (the one that actually is in that paragraph) $R_{T}$ shouldn't include $R_{x}$ and this is not clear from there. I also took the values from an exercise on the book and I checked with Python that both the methods work.

>>> def par(*res):
... return 1 / sum(1/r for r in res)
>>> r1 = 10
>>> r2 = 2
>>> r3 = 20
>>> it = 4
>>> # i1 should be equal to 0.6154 ampere
>>> # method 1
>>> rt = par(r1, r2, r3)
>>> (rt/r1) * it
0.61538461538461531
>>> # method 2
>>> rt = par(r2, r3)
>>> (rt/(r1+rt)) * it
0.61538461538461531

As you can see in the method 2 there are only R2 and R3. —Preceding unsigned comment added by 130.232.126.213 (talk) 20:24, 11 October 2008 (UTC)

Looks like your mistake is that you included $R_{x}$ in $R_{T}$. Both your book and the article are correct, they just have different definitions of $R_{T}$.

I like your use of Python BTW. I believe there are a couple circuit simulator libraries written in Python, though I haven't tried them yet. -Roger (talk) 19:38, 12 October 2008 (UTC)

I know that both the ways are correct, I was just pointing out that from that paragraph is not clear that $R_{x}$ mustn't be included when you calculate $R_{T}$. Usually when you calculate $R_{T}$ (total resistance) you include all the values, but with that formula you have to omit $R_{x}$. I think it would be better to show both the methods and explain that they have different definition of $R_{T}$. I also find $I_{x}={\frac {R_{T}}{R_{x}}}I_{T}$ simpler, you can find all the currents just changing the value of $R_{x}$ without having to change and recalculate $R_{T}$ (with $I_{x}={\frac {R_{T}}{R_{x}+R_{T}}}I_{T}$ you have as many different $R_{T}$ as the number of resistors in the circuit), moreover you often already have the total resistance. —Preceding unsigned comment added by 130.232.126.213 (talk) 00:03, 21 October 2008 (UTC)

I think there still is an error. Take the example ${\frac {R_{T}}{R_{T}+R{X}}}I_{T}$, for two resistors in parallel. If we do this, and note that ${\frac {1}{R_{T}}}={\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}$ we get, by insertion, $I_{1}={\frac {({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}})^{-1}}{({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}})^{-1}+R1}}I_{T}$, and extending with $({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}})$, we get: ${\frac {1}{R_{1}({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}})+1}}I_{T}={\frac {R_{2}}{2R_{2}+R_{1}}}I_{T}$, which is NOT equal to what the textbook gives us, which is, as noted above, ${\frac {R_{2}}{R_{2}+R_{1}}}I_{T}$, for the case of two transistors in parallel. So we should either change the definition for $I_{T}$ in the article, or write another formula for the voltage division (the equation for division and the definition for equivalent resistance are inconsistent).

RTotal -> RX

Can someone please double check I was correct in making my last edit? I changed RTotal to RX — Preceding unsigned comment added by 2601:880:C100:69D0:C414:6EEF:8F2A:646A (talk) 22:50, 7 December 2016 (UTC)

You are correct. I just double checked the simple derivation from Ix Rx = (IT - Ix) RT. digital_me (talk) 23:51, 5 February 2017 (UTC)

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Possible error

Hi! A friend of mine has pointed out to me that maybe $I_{X}={\frac {Z_{T}}{Z_{X}}}I_{T}\$ should be edited in $I_{X}={\frac {Z_{T}}{Z_{X}+Z_{T}}}I_{T}\ ,$ and $I_{X}={\frac {R_{T}}{R_{X}}}I_{T}\$ in $I_{X}={\frac {R_{T}}{R_{X}+R_{T}}}I_{T}\$, and the sentence "where Z_T refers to the equivalent impedance of the entire circuit" is probably wrong. Could someone have a look? Thank you, --Epìdosis 10:32, 20 May 2019 (UTC)

In response to above: I believe both are correct. But the original form of $I_{X}={\frac {R_{T}}{R_{X}+R_{T}}}I_{T}$ is (in my mind) extremely confusing. While Nilson/Riedal use this form (I went and checked my copy as I didn't believe the reference at first), every circuit division rule I've seen (besides this one) uses the form of $I_{X}={\frac {R_{T}}{R_{X}}}I_{T}$, because in general, $R_{T}$ always refers to the entire circuit (or at least, the entire parallel portion). Defining it to be the other way is just... odd. GetaR (talk) 00:56, 19 January 2020 (UTC)