# What is Circuit analysis: Definition and 548 Discussions

A network, in the context of electrical engineering and electronics, is a collection of interconnected components. Network analysis is the process of finding the voltages across, and the currents through, all network components. There are many techniques for calculating these values. However, for the most part, the techniques assume linear components.
Except where stated, the methods described in this article are applicable only to linear network analysis.

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1. ### Measuring the inductance of a micron feature size gold coil

Hi all, I recently fabricated a bunch of gold coils patterned onto a glass substrate and am in need of measuring the inductance of these samples. Since the feature size is in microns, I can't exactly use an RLC meter. At the moment, I'm trying to build an LCR series circuit with a PCB and...
2. ### Circuit analysis via polyhedron

(NOTE: I should state that my circuit analysis knowledge is up to the level of a single comprehensive EE course, as per ME students.) I was thinking about the famous resistor cube problem, and I've come up with some observations: - Every branch (I think that's the term - i.e., a branch is any...
3. ### Capacitor circuit analysis

Figure: My attempt at a solution: Once the capacitors have been applied, we see directly that ##\boxed{v_c=v_0=0\, \textrm{V}}## Wouldn't this one be done like this? I know the following: in a circuit with capacitors and coils, if we have Capacitor: we change for an open circuit. Coil: we...
4. ### Finding the Thevenin voltage

Hello I'm trying to solve my homework assignment, I have successfully found the thevenin resistance which is equal to 3.75 but I'm stuck on how to even get started to find the voltage because there are too many components. I have shorted the load resistor which is called RL but there are too...
5. ### Engineering Need help answering questions (Voltage source and 3 Resistors)

Hello. I need help arriving to the answers to the following question above. You will find the circuit attached for Number 1 I though that crrent would be maximum when resistance is replaced with a wire but I couldn't get a an expression for ut. as for question number 2 I tried applying node...
6. ### Engineering How do I find Vth with the node voltage method?

Hello. I'am practicing circuit analisis about the norton and thevenin's circuits and I can't seem to manage to get the right thevenin's voltage using the node voltage for a) resolution 1) I did source transformation turning the current source(2A) into a voltage source (10V) applied node voltage...
7. ### Engineering First Order RL Circuit: Finding a Current I2(0-)

I shorted the inductor and performed mesh analysis. The solutions to the linear system were done using a calculator. The book says that the value for i2(0-) should be 15 mA but I'm getting -2mA. What am I doing wrong? I'm completely confused. Maybe mesh isn't the most efficient way to find I2...
8. ### Engineering Circuit analysis on a supernode

Hello. Can someone give m e pointers on how to find the value of vx given that it is inside a supernode(will it be the valueof the voltage inside or the difference of potential between the two nodes?): here's the exercise and what I've done so far attached. Your time and attention are deeply...
9. ### Engineering Opamp subtractor circuit

So after using superposition and setting the ratio R2/R1 = R4/R3 the same or R2=R4 and R1=R3,i come to the eq. for output voltage Vout= R2/R1 * (V2-V1) or R4/R3(V2-V1). And in the book foundations of analog and digital electronics by agarwal and lang, they are saying that this circuit is a...
10. ### Engineering Opamp adder circuit: Where does the "-" come from?

So i used KCL and both currents are flowing into the node, and then leaving together to go to the resistor R3. So my eq can be seen in the picture. I was looking in a book and they had a minus infront of the parantheses. Is the current flowing from R3 into the node??
11. ### Engineering OPamp circuit - how to simplify this term?

So this is the circuit. And here i tried to calculate Uout/ Uin , any suggestion how to simplify this term?? I used Uout= Uin * (1+ Z2/Z1)
12. ### Engineering Constant current source transistor circuit - differences between 2 types?

So basically we can have a constant current but i don't understand this circuit. for example: i can have the Ia what ever I want with current divider rule: Ia = Iq * R2/R3. So Ia is proportional to the ratio of R2/R3. And if i give a resistor at the collector terminal, if i change it between...
13. ### Engineering Op amp circuit -- Did I calculate the output voltage correctly?

can someone check, if i calculated the output voltage correct? i used virtual ground because V+-input of the op amp is 0 --> V- input is then also 0.
14. ### Simple voltage divider -- why does this work?

Summary:: don't understand how can we use a voltage that has been already dropped. I don't understand the voltage divider. So R1 and R2 are the same. I have 10 V in beginning, then 5V drop across R1 and then i have 5V drop across R2. But how can I use the 5V if they already dropped at R2? If...
15. ### Engineering Black box which contains 5x 1ohm resistors

You are given a black box with three terminals, as shown below. The box is known to contain five 1-ohm resistors. Using an ohm-meter, you measure the resistance between the terminals to be the following: A - B: 1.5 ohms B - C: 3 ohms A - C: 2.5 ohms Determine the configuration of the five...
16. ### How to use Kirchhoff's voltage law on this circuit?

In this circuit, I have to find the potential at point O. I tried using Kirchhoff's voltage law for the three open loops AOC, AOB and BOC to arrive at potential at O. According to my calculations the potential at O should be 0, but that is not the case according to the source. So I must be using...
17. ### Superposition Principle for two Voltage Sources (confusions about....)

I have a question about natural limitations when the superposition principle for circuits is applicable. Possibly there is a quite elementary reason why the problem I'm going to present next fails, but up to now I haven't a precise reason why that's exactly the case. Could somebody help...
18. ### Find frequency such that two components have same average power

(This is my first time posting here, sorry in advance for any difficulties. ) All componenets of same type has same magnitude, so e.g. the two resistors both have $R$ resistance. Given the difficulty of the previous exercises, I believe I'm over complicating the problem. However, here is what...
19. ### AC circuit analysis involving resistors and inductors

Summary:: Hi anyone can explain me how to solve this circuit, finding the current I2 and I1? Really don't know where to start Thanks
20. ### Receiver Circuit Question -- What role does this antenna capacitor play?

Which role plays an additional capacity in a receiver circuit between the antenna and the matching-box part like in this example (found in https://www.frostburg.edu/personal/latta/ee/twinplex/schematic/twinplexschematic.html): Is it necessary for this receiver circuit or just optional? What...
21. ### Which lamp is dimmed in the circuit?

The true answer is B. But I don't understand why! I know: Kirchhoff's circuit laws : ∑In=0 If we assume that a current that goes from plus to minus, before it passes through lamp B, I know that according to Kirchhof's laws, part of the current will pass through the bottom path where there is...

24. ### DC current through a resistor circuit

Summary:: Current through a certain resistor in a mixed dc circuit. Hi, Sorry if this is the wrong forum. I'm trying to work out the current through R1.The answer I need is 2 Amp, which I have confirmed with a simulation software. I have calculated the source current as 8A, the current past...
25. ### Circuit Analysis Theorem For the Number of Independent Equations

I attached a screenshot of the book (sorry no pdf available for this book). Right above the somewhat central line they give the theorem that if there are m currents and n nodes, then there will be n - 1 independent equations from the current law and m - n - 1 from the voltage law. I count 4...
26. ### I Checking for negative feedback in a circuit

This is the circuit in question. During lecture, when checking whether this was negative feedback, my instructor said that if the v_out increases, then v- increases as well, which would lead to the next v_out decreasing because v_out = A(v+ - v-). I get how if v- increases the next v_out would...
27. ### Confused about a Result (Circuit Analysis)

The problems I am referring to are problems 4-10 and 4-11. There is no solution provided for 4-10, so I want to check my answer here. However, I don't understand the answer to problem 4-11. Shouldn't it also be 24 V since it is in parallel with the 200 k##\Omega## resistor? I am actually...
28. ### Electric Circuit Analysis, Nodal Analysis and finding Voltage.

Summary:: The image shows two circuits, in the first one, using Nodal Analysis we find that V1=4.8V, but in the second circuit V1=10 because using KCL - 10+V1=0. I understand what happened in the first circuit, but I don't understand what happened in the second one, they look the same to me...

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30. ### PWM signal generating circuit based on LM393

This is a PWM signal generating circuit based on LM393. When I was running this LM393 circuit, I found that this circuit only consumes about 10 milliwatts of power at a voltage of 5V. Not only that, this circuit can work normally at 3.3V, 12V and 18V. But later I found that this circuit...
31. ### Engineering W0 = 1/RC? Transfer Functions and Bode Plots

Here is the example and solution in full. I have circled where I'm at and highlighted the part that's tripping me up. I managed to get... and getting everything in terms of the angular frequency seems to be critical for getting the plots for the Frequency Response. I checked my notes on RC...
32. ### Help finding Thevenim Equivalent - Circuit Analysis

Summary:: So I found Vth=1.19 using Nodal analysis and I'm not sure if that's right, I'm trying to find Rth now but I'm confused as to what to do, any tip that tells me at least from where to start is appreciated. Edit: so I did 12||60 so Rth=10 ohm, is that correct? Is Vth correct too?
33. ### RLC Circuit Analysis -- Two sources and two switches

Hello, this is my working. My professor did not give any answer key, and thus can I check if I approach the question correctly, and also check if my answer is correct at the same time. When t < 0, capacitor acts as open circuit, $$V(0-) = V(0+) = 9V$$ When t = infinity, $$V( ∞) = 5V$$ (because...
34. ### Engineering Circuit theory: capacitor energy storage and discharging/charging times?

This is not my homework. I took it upon myself to answer a textbook question for mental stimulation. I wanted to know if someone can verify if these were the correct values that needed to be solved for, process, and final answer, and if not, what needed to be considered. For the initial...
35. ### Engineering [Circuit Analysis] Am I on the right track with this problem?

*A is the node all the way to the left above the 30V but I didn’t end up using it because I don’t think you need it since the same as 30V, right? * I know I messed up somewhere because shouldn’t V1-4 = 30? After finding my V1 I used that value to find the other Vs and it ended up being close to...
36. ### Calculating the resistance in a compensating circuit for a thermocouple

Homework Statement:: A K-type thermocouple is connected as shown to sense temperature. The temperature zone is at 25°C. The RTD has a resistance of 100 at 0°C and a TCR coefficient of 0.00385. A 5V power supply drives the circuit. Calculate R2 for proper compensation. What is the emf produced...
37. ### Circuit problem with two sources and three resistors (Nodal Analysis)

Ans: 0.123A Tried mesh analysis and got it but didnt for nodal analysis

I'm reading this chapter in Electrical Engineering book regarding AC circuit analysis where there is a solved example which I've attached, but there are some concepts that are confusing me. First, why and how do we know that the phasor value of voltage is: -pi/2 Note: I do understand that...
39. ### Finding the resonant frequency of this "discriminator" demod circuit.

This is the FM demodulation "discriminator" circuit. It is one of the simplest analog demod setups one could think of. An RF (FM) voltage signal is applied at V12 and the voltage at ' a' ' is supposed to contain the AF signal in its amplitude. The idea behind the circuit is that it resonates at...
40. ### Intro Physics Textbook on Electronics and Circuit Analysis

Hi folks, I'm looking for a solid introductory book on electronics and circuit analysis. I have seen The Art of Electronics highly recommended. I will likely get it but as a supplement. Does anyone know of any other good electronics textbooks? I don't mind old textbooks. Some of the newer...
41. ### Circuit theory - Resistor function for dynamic non linear circuits

Hi, I'm reading the following paper (L. Chua) about the state-of-art of dynamic non linear circuit analysis -- Chua_Dynamic_Circuits I've a doubt about Theorem 2 on section 3.2 On the Existence of the Resistor Function that establishes sufficient conditions for the existence of network...
42. ### Voltage restriction for nodes on the same branch?

originally ,I want to prove (TT:current can only flow from c to d),thus I try to figure out what will happen if Vd >Vc,then I label corresponding current direction.Afterwards,I know what's wrong: (A:current doesn't flow out of d ),then I attempted to prove A ,yet I consider that A might not...

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45. ### Engineering Circuit Analysis -- How many independent equations can be written using KCL?

I think there are 4 essential node. So we can write 3 KCL independent equations.
46. ### Checking Kirchhoff's current law

Im trying to apply KCL to the serial c and parallel rl circuit. IZ = = = 330.562 mA but this means incorrect proof. Anyone can help please?
47. ### Electrical How to wire an LED switch based on rated voltage and current

Could someone please help. i need to connect a 12vdc motor which can draw 16 amps to a switch that has an led on it. the led is rated at 3v 20mA. The power supply i am using is rated to put out 12vdc at 30A I thought of the possibility of adding a resistor to the positive pole of the led. In...
48. ### Engineering Understanding the output waveform and using LTSpice

For the following circuit I need to find the output waveform. A. Conceptually I am at sea here but I will have a stab at it. My though process is as follows : At a given instant, the AC voltage is at a fixed value and this value drops (##V_drop##) across the resistor ##R##. The voltage...
49. ### What approach should be used when solving a circuit?

I am close to graduating as an EE major but I have never been able to organize a step by step method on analyzing a circuit. It seems to me that every time I am trying to analize a circuit I end up with a bunch of equations and nothing more. I know that I should: 1. Know what I am solving for...
50. ### Physical/conceptual reason for inductor voltage step response

I'm trying to understand the physical reason why when you drive an ideal inductor (no series resistance) with an ideal voltage step input (no series resistance), e.g. some Vin(t) = V0u(t), the output current will be a linear ramp. I can see how to derive this from the inductor equation, v = L...