Electronics > Beginners
Calculate value Resistante through voltage divider
Jasonbit:
Hello,
How can I isolate the x, in this fraction? https://postimg.cc/xNV8665j
I am trying calculate the value of R2 through voltage divider (https://www.electronics-tutorials.ws/resistor/res10.gif)
I only need the value of the R2, because I have the value Vout, Vin and R1. This question is relative mathematic, I know, but I spend many hours try search about this theme around the web. (Actually, I do not even know how to search...)
Thanks
RandallMcRee:
Umm
search for "voltage divider calculator".
Lots to choose from.
Wimberleytech:
http://www.ohmslawcalculator.com/voltage-divider-calculator
pigtwo:
I think OP is just asking how to solve the equation.
It is not possible to isolate x in the expression x/(x+y). This is as simple as that expression can be. But if you put it into an equation you can solve for x.
You're trying to solve something like 3.3 = x/(x+y) correct? The first step for solving for x would be to multiply the denominator of the right side(IE x+y) to both sides. This will remove the fraction and from there you can solve for x using addition/subtraction operations.
Zero999:
--- Quote from: Jasonbit on October 18, 2018, 10:45:41 pm ---Hello,
How can I isolate the x, in this fraction? https://postimg.cc/xNV8665j
I am trying calculate the value of R2 through voltage divider (https://www.electronics-tutorials.ws/resistor/res10.gif)
I only need the value of the R2, because I have the value Vout, Vin and R1. This question is relative mathematic, I know, but I spend many hours try search about this theme around the web. (Actually, I do not even know how to search...)
Thanks
--- End quote ---
How about solving it from an electronics perspective, rather than an algebraic method?
You know VIN, VOUT and R1, therefore you can calculate the current through R1 using Ohm's law. The voltage across R1 is equal to the difference between VIN and VOUT, since potential differences are relative.
I = (VIN-VOUT)/R1
The current in both of the resistors is equal, since they're in series so R2 can be calculated using Ohm's law.
R2 = VOUT/I
And there's your answer.
If you put both of the above equations together, no doubt you have a similar result to what one would have got using algebraic manipulation.
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