Questions tagged [kirchhoffs-laws]

Kirchhoff's circuit laws deal with the conservation of charge and energy in a circuit.

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3answers
583 views

Can two voltmeters connected to the same terminals show different values? Circuit with induced EMF

The circuit shown below consists of two resistors connected in series that form a closed loop. No electrical sources are in that loop.Let’s assume that the resistance of the wires that connect the ...
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3answers
56 views

Applying kirchoffs law in a simple circuit [closed]

Can we apply Kirchhoff's volatge law in this simple circuit and say V1=-r1I1 and V2=r2I2 or is there an other connection between voltages and currents?
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Circuit modeling a biological cell potential difference

From a book on Neuroscience, Go to page 12, Box 7-2 (particular image attached below) The author claims that $$V_m = E_{Na} + I_{Na} / g_{Na}$$ on one side of the equation and then says $$V_m = E_{K} ...
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1answer
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Node Method vs Simple KVL and KCL Equations Difference

I am just quite confused when deriving some equations for this simple circuit. Using just KCL and KVL (loops in green) to the best of my understanding, I get the first set of equations. Firstly, are ...
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1answer
100 views

Measuring the voltage drop across electrical components doesn't match the calculated values

I have a newbie question regarding circuit analysis. I have a simple circuit with a voltage source of +4.32V (output of a u7805C voltage regulator), an 18K Ohm resistor, a normally open push button, ...
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Why don't we consider VCE voltage here when we calculate the current?

This is class B Push-Pull circuit for an amplifier. The question says: Calculate the maximum Icmax current of the resistance RL if you knew Rl = 8Ω The book solved it this way: Vcc - (Rl * Icmax) ...
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2answers
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Adjusting buck regulator with DAC

I have a buck regulator (say the TPS82085) which I would like to use to regulate a 5V supply to various values ranging from 1.2V to 3.3V. It seems that a DAC is a good way to do it (I initially ...
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3answers
120 views

Which technique do I use to solve this problem?

I'm currently working on open questions for my Physics 2 exam about eltric fields, magnetic field, circuits and so on. I'm currently stuck with this problem: I'm asked to solve for the voltage $$U_X$...
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Meaning of the three bars on a circuit and help regarding Kirchhoff's Laws

So i'm really lost and I have to solve some problems from circuits regarding mainly resistors. I have this circuit and I am a bit lost because I don't really understand what to do to find the value of ...
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2answers
76 views

Transfer Function of Electrical System

I am trying to find the transfer function \$\frac{V_{out}(s)}{V_{in}(s)}\$ of an electrical system that operates according to the diagram below. \$V_{in}\$ is switched between 0 and 13 Volts (i.e \$...
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1answer
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how do i find the resistance R in this? I tried using kvl and kcl but still not able to find the answer

I have tried it with kcl and kvl but not getting the answer. Then i tried with mesh analysis.But no good. Any help will be greatly appreciated.
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Kirchhoff's Voltage Law Yields More Variables Than Equations

When I try to solve this problem I get three equations: VR3+VR5=20 VR1+VR3=-20 VR1-VR5=-40 The problem is that you can obtain 1. by subtracting 3. from 2. so you actually have only two equations ...
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Lumped Circuit Abstraction extreme cases

When using lumped circuit abstraction, if we consider two ends of a voltage source connected with ideal wire KVL won't hold; and also if we put two current sources opposite two each other, then the ...
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3answers
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Trouble understanding when voltages get split

I am having trouble solving this Op-Amp problem. I'm looking for Vo, and am confused as what to do with the 9V supply and the 2k and 6k resistors. Would the 9V be split between these two resistors? ...
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330 views

More equations than unkowns in amplifier circuit

I am trying to find the Magnitude Response of the gain of this amplifier circuit. The gain formula is: $$ H(\omega) = \frac{\tilde{V_{out}}}{\tilde{V_{in}}}$$ My amplifier circuit is as follows:...
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Solving an ideal opamp-circuit leads to a contradiction

Well, I am trying to analyze the following circuit: simulate this circuit – Schematic created using CircuitLab When I use and apply KCL, I can write the following set of equations: $$ \begin{...
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1answer
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Circuit analysis by local application of Kirchhoff's current law and Ohm's law

First of all I want to say that this is a new field for me, so please excuse any inaccuracy in the used terminology and the lack of understanding of some concepts. I am trying to understand whether ...
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31 views

How do I solve using nodal analysis when there is a battery before the resistor?

I need to use node analysis on the following circuit. I am confused as to how to solve node 1 as there is a battery of 3V between the node and 4 ohm resistor. Should I solve for it?
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1answer
43 views

Circuit with dependent source confusion

Can we find the value of \$i'\$ in this circuit, considering \$I\$ and \$R\$ are known? Using Kirchhoff’s Current Law we have that \$I = i + i'\$. If the dependent source voltage was \$ki \;, \; k \...
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Kirchhoff's laws in an open circuit

I am currently struggling with the following homework problem: It asks to find the voltage across the points a and b. I first redesigned the circuit to make it look for straightforward and I ...
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3answers
135 views

How Does Kirchoff's Law Make Sense

I understand the algebra, and I can also use Kirchoff's Law in calculation. But I struggle to understand how it makes sense logically. The law states, that the sum of the currents entering a ...
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1answer
46 views

Find all the Kirchhoff's circuit equations in a multiple batteries circuit [closed]

So I saw this exercise where it says to find all the currents that flow in the circuit and all the equations for the currents and voltages. Any help would be more than welcome]1
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1answer
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Converting a schematic to a graph [part 3]

This is part 3 in my journeys to try and graph a basic resistor circuit programmatically (part 1 and part 2. I think I have finally figured out how to treat components -- which if I looked at any ...
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1answer
67 views

Determining gain, KCL/KWL (Basics)

Below is a pi model schematic of a cascaded amplifier. The goal is to find the gain with Rp as load. So the gain would be: \$ A = \frac{V_{out}}{V_{in}}\$. So i set out to find \$V_{out}\$ in terms ...
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124 views

How do we know that current doesn't get “stuck” in junctions?

I know the question might sound slighly basic, but stay with me here. Kirchoff's Current Law states that "The algebraic sum of currents in a network of conductors meeting at a point is zero." ...
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1answer
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Converting a schematic to a graph

This is a follow up to the question about I posted last night, Converting a schematic into a graph. From some of the answer, I was able to re-work how the graph is done -- with components as edges and ...
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Single phase neutral current & three-phase neutral current with respect to kirchhoff's law

In the below schematic, would be the sum of all current in the single phase neutral wires equal to the current in neutral wire going to the 3 phase main disconnect? In theory, we know that if the 3 ...
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2answers
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Converting a schematic into a graph

I've been working for some time trying to figure out how it might be possible to translate a schematic into something like a node graph, where each node is a component. I've taken some liberties in ...
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1answer
44 views

Node analysis: estimating variable current branches

Is there a way to get the number of potential currents that could be in a circuit? (Note: in the following circuits ignore the Resistor value, I've just added a resistor with the default schematic ...
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1answer
31 views

Verification of power law

Here is the solution that I have so far. How are the values of Vx different if we solve it using KVL and different if we use Ohms Law? And to verify the power law, do i need to calculate the ...
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1answer
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I need to verify the power law in this question

Question. I suppose the value of Vx must be positive. So how do I manipulate the equation such that Vx becomes positive? Can this be the solution to this question?
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What exactly is this question asking us to do?

Based on the model and circuit shown in Fig. 2, draw a circuit model of the path of current through the human body for a person touching a voltage source with both hands who has both feet at the same ...
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1answer
163 views

How do I calculate i, i1, i2 and v2?

I'm unable to figure out how to use the current dependant voltage source in KVL The following are the equations I've found, up till now: 20i+V2=10, V2=50i1, 20i+50i1=10, i=i1+i2
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Solving for current with voltage drops

Given the following circuit: Why is the current through the circuit 34.7mA instead of 35 mA? My thinking was that: The LED draws two volts, so it effectively makes the battery 7V instead of 9V. ...
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1answer
42 views

the transconductance of cascade MOSFET IF channel length modulation is NOT ZERO

What would the derivation of the cascode MOSFET transconductance in small signal analysis IF THE CHANNEL LENGTH MODULATION IS NOT ZERO, as most examples for the cascode mosfet transconductance say in ...
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1answer
33 views

Lumped model not applying to PCBs

Recently I have heard that KCL and KVL do not fully apply when performing electrical measurement on PCB traces. It was implied that PCBs are not completely lumped circuits - that is, we cannot assume ...
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4answers
126 views

Reasoning behind equations in analysis of electrical circuit

I am currently studying the mathematics textbook Nonlinear Dynamics and Chaos by Strogatz. As part of an example, I am provided with the following electrical circuit and accompanying explanation: ...
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2answers
73 views

Solving simple parallel/series without Req

Given the following circuit with three resistors, R1=100Ω, R2=200Ω, R3=300Ω: To solve this using the \$R_{eq}\$ trick: ...
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1answer
129 views

Substitution + Superposition with RLC circuits

Consider the following circuit: simulate this circuit – Schematic created using CircuitLab \$E\$ is a constant voltage source. The switch is closed at time \$t = 0\$. The request is to ...
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2answers
83 views

Number of independent KVL and KCL

I know that the number of KTL and KCL is related to the number of nodes \$N\$. For KCL there are \$N-1\$ equations while for the KTL there are \$L-(N-1)=L-N+1\$ equations. However I didn't understand ...
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3answers
104 views

Circuit Analysis of an Outlet Tester

I have an Outlet Tester like this: It is used to see the mains electric connection, it has the next states: I opened it and then I reversed engineer it. The diagram I obtained is this: I would like ...
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2answers
35 views

Position of the voltage source with parallel resistors

In the following circuit I want to calculate the current flowing through the voltage source (node A) simulate this circuit – Schematic created using CircuitLab If I use the KCL I get \$I_A = ...
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3answers
92 views

Current flowing in a short circuit with a voltage source

I want to calculate the current flowing in the node A of the following circuit: simulate this circuit – Schematic created using CircuitLab This can be approached in several ways. The tension ...
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1answer
58 views

Kirchhoff's Laws exercise

So I am solving this exercise. The problem given is to calculate the Voltage between ab. I calculate to 16V but the answer is 4V. I found out that they did not include Voltage between eb. I wonder why ...
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In search for more Exercises

I'm currently studying in Germany for Electrical Engineering (course in English). Due to incoming exam, I am looking for more exercise material as although my course is in English, the school library ...
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1answer
42 views

Why doesn't KVL work for the bottom loop?

I was doing a practice problem. I calculated the correct value for i_a = -2.4 A. But I used KVL on the bottom loop to get R, and got the inverse of the answer that I actually needed. My equation was -...
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137 views

Simple circuit analysis with node potential method

I can't find the correct solution for this exercise and I can't figure out why. simulate this circuit – Schematic created using CircuitLab The question is: What is the current \$I_3\$ ? (...
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1answer
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Difficulties in KVL signs (RL circuit)

If we start from bottom left and rotate clockwise, then first we visit resistor negative terminal so I expect -Ri but the book says the below equation: So why ...
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2answers
192 views

Correct equation for describing *exactly* the output of a current follower

In the textbook I use for teaching Instrumental Methods to Analytical Chemistry, there is a discussion about current follower circuits based upon the following figure: After describing the ideal ...
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Dependent current source Mesh Analysis challanging problem

\$I\$ \$2\$ gets different value by different equations , Using mesh analysis . Please explain why \$I\$ \$2\$ has two different values using mesh analysis . My approach : \$-12I1+2I2=0\$ \$-2I2+...

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