Electronics > Projects, Designs, and Technical Stuff
Reading high currents on PCB: Hall effect sensor vs shunt resistor
Siwastaja:
--- Quote from: engrguy42 on May 07, 2020, 07:37:54 pm ---I'm cornfused....
A true calculation of resistance includes considering the temperature coefficient of resistance, doesn't it? And if it's negative like semiconductors, that will change the value of resistance. How is that BS?
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If a resistor has such strong negative temp coeff that it causes practically all current go through one resistor with only minor imbalance in resistance, such part is crappy beyond imagination and could hardly be called a resistor; it would be a semiconductor, or maybe an NTC.
I was commenting about the phrase "current flows through the path of least resistance", which is just simply untrue and makes no sense whatsoever. Whoever came up with that wasn't thinking temperature coefficients or other sophisticated details; in fact, they just were not thinking at all, and then it stuck. Current is shared between the resistive paths in a simple linear fashion, I = U/R where U is the same over all paralleled resistors. So if you apply 1V over 0.9 ohm and 1.1 ohm resistors, the currents are 1.11A and 0.91A, respectively. The sad thing is, this is so easy to analyze properly that no one needs to invent such a "helpful" phrase.
engrguy42:
--- Quote from: ejeffrey on May 07, 2020, 08:19:30 pm ---What he is referring to is the common misunderstanding by those new to electronics of the phrase "current follows the path of least resistance" to mean that when there are resistors in parallel the current only flows through the smaller one. In reality we know the parallel combination of to resistors is smaller than either and the "least resistance" path is to flow through both.
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AAAAhhhhh, that's what he meant. I never considered that some people think that ALL current flows thru the smallest of two resistors in parallel. Thanks.
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