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That is were I intend to use this example. Except: for Thevenin I need to calculate exactly this substitution resistance. So how do you calculate this substitution resistance for this example?I can think of at least two ways to calculate the total resistance - thevenin substitution or kirchhoff laws.
How do you calculate the "equivalent" of R1 and R3 when there is R5 in between?I would transfer R1-R3 to its equivalent, and R2-R4. Now you get a series circuit Vt13 - Rt13 - R5 - Rt24 - Vt24. From that you get current through R5 and voltages at both sides of R5. Find the rest of the currents and then plop the whole mess into ohms law and get the total resistance of the circuit.
Do you mean the Thevenin resistance, also known as the output resistance between Vcc and ground?What is the correct way to calculate the substitution resistance of the schematic attached?
Interesting. Can you give plse a shortcut or link on how to perform mesh analysis? Thks!I would do mesh analysis and pull the equivalent resistance out of that. R5 is practically made for that here. Parallel/series resistor simplification, thevnin, etc are shortcuts, not fundamental methods and so have their limitations.
Method 1: this schematic is actually the result of having this actual voltage source shorted out and the resulting schematic is what is shown in post 1.Do you mean the Thevenin resistance, also known as the output resistance between Vcc and ground?
Method 1) Insert an independent voltage source in series with R3 and ground. Calculate the output voltage Vcc. Then calculate the current of Vcc with it shorted to ground. Using the definition of resistance, the equivalent resistance is Vopen/Ishort.
Method 2) Insert a 1 amp independent source at terminals of Vcc and ground. Then calculate the voltage of Vcc. The voltage value will also be the resistance value because you are using a 1 amp current source
Ratch
You showed me a schematic, I described two methods to obtain a result.Method 1: this schematic is actually the result of having this actual voltage source shorted out and the resulting schematic is what is shown in post 1.
Then follow what I described.Back to square 1: I need the equivalent resistance of what is shown in post 1.
Assume 1V on the input if you please, it makes life a bit easier. Thevenin equivalent of R1 and R3 (with 1V applied) is a Vt13=0.6V source with Rt13=12 ohms in series. Equivalent to R2-R4 is Vt24=3/7V and Rt24=30||70ohms in series. Now you have a simple circuit with two voltage sources and three series resistors, Vt13 - Rt13 - R5 - Rt24 - Vt24. Get current through R5, and backtrack to get current through the rest of the resistors. Then calculate the total resistance from R=1V/Itotal.How do you calculate the "equivalent" of R1 and R3 when there is R5 in between?
You cannot have it in series, and not with R5 in parallel because R5 belongs to the R4 and R2 branch.
Lile this (attached)? By the way: Rt24 = 30||40 ohms, not 30||70?Assume 1V on the input if you please, it makes life a bit easier. Thevenin equivalent of R1 and R3 (with 1V applied) is a Vt13=0.6V source with Rt13=12 ohms in series. Equivalent to R2-R4 is Vt24=3/7V and Rt24=30||70ohms in series. Now you have a simple circuit with two voltage sources and three series resistors, Vt13 - Rt13 - R5 - Rt24 - Vt24. Get current through R5, and backtrack to get current through the rest of the resistors. Then calculate the total resistance from R=1V/Itotal.
This has everything you should need:Interesting. Can you give plse a shortcut or link on how to perform mesh analysis? Thks!
Show below are 3 solutions. The first solution is a mesh solution for the Vcc loop on the left side of the circuit. The second solution is a mesh solution for the Vcc loop on the right side of the circuit. The third solution is my method 2 suggestion from above showing a node solution with a 1 amp current source applied to the Vcc terminal. The calculated voltage value of the third method is the same as the impedance because the current source is 1 amp. Better learn how to use these methods or you will wander around in a wonderland of perpetual fog. All the methods below use 3 equations and solve for 3 unknowns.Lile this (attached)? By the way: Rt24 = 30||40 ohms, not 30||70?
Please can you explain?(...) After that, calculate the voltage at points left and right of the R5 - those are the same voltage as in the original schematic. (...)
Hi Ratch, I greatly appreciate your input! However you use Kirchoff's laws resulting in 3 equations with 3 unknowns, which I understand. But here I specifically want to use equivalent voltage source and equivalent substitution resistance based on Thevenin theorema.Show below are 3 solutions. The first solution is a mesh solution for the Vcc loop on the left side of the circuit. The second solution is a mesh solution for the Vcc loop on the right side of the circuit. The third solution is my method 2 suggestion from above showing a node solution with a 1 amp current source applied to the Vcc terminal. The calculated voltage value of the third method is the same as the impedance because the current source is 1 amp. Better learn how to use these methods or you will wander around in a wonderland of perpetual fog. All the methods below use 3 equations and solve for 3 unknowns.
View attachment 114842
As you can see, the impedance is 685/24 ohms.
Ratch
Sorry missed those currents before, not sure where those are in the schematic.Please can you explain?
Using Thevenin I understand your reasoning for Vt13, Rt12, Vt24, Rt24. But to calculate the voltages left and right of R5, and taking my reasoning for points 1 and 2 is correct ( ie: I1 = (0.6 / (12+10+17) and I2 = (3/7) / (12+10+17) ) , what schematic must be used for that calculation?
If understand well, using Thevenin:Sorry missed those currents before, not sure where those are in the schematic.
Voltage between R1,R3 and R5 is the same as between R6, R7 and R8. So if you know voltage at that point, you also know current through R1. Do the same for R2, add the two together and you get the total current.