Questions tagged [kirchhoffs-laws]

Kirchhoff's circuit laws are important for circuit analysis. There are two laws: Kirchhoff's Current Law (KCL) and Kirchhoff's Voltage Law (KVL). KCL states that the sum of currents flowing into a node is zero, and KVL states that the directed sum of voltages around a closed loop is zero. Consider also using the "circuit-analysis" with this tag.

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Current Direction and Voltage Polarity in Capacitor/Inductor Circuits

I believe that this question may be simple for those with a little more experience, but it is still puzzling me. Studying capacitance/inductance, I understand that the capacitor in the DC case behaves ...
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Temperature gradients and different types of wires in thermocouples

I use long (10-m) copper-constantan thermocouples for work to measure temperature. The temperature gradient is only present in the 15 cm nearest the hot junction; the remaining 9.85 m of these ...
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How do I find Vs in this circuit with a 2:1 ideal transformer?

How do I find Vs given that V0(to the left) is 10L30degrees? I started by finding that the current on the 10 ohm resistor is 1L30 degrees, and then using kirchoff's law, the current on the tranformer ...
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Problems regarding KCL & KVL

Question: Below figure represents an approximate equivalent circuit of a field effect transistor amplifier. Using KCL find the output voltage \$v_2\$ in terms of input voltage \$v_1\$. My try: I ...
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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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Circuit Analysis: Difficulty in obtaining a current through a resistor?

I'm solving a problem that requires I compute some impedances, and then the current through a resistor. I obtained some of the impedances*, but don't know how to get the second part (current). ...
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Confusion with applying KCL to three phase delta connection

Below is a 3-phase delta connected for balanced loads Z: Since phase to phase voltages(voltage across loads) have 120 degrees phase differences and since the loads have the same impedance we can ...
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Double loop, double voltage source circuit analysis problem, with three unknown voltages/currents, using Kirchhoff's laws and Ohm's law [Post #2]

I recently asked this question: Find the currents and voltages in the circuit shown in Fig. 2.28. Answer: \$v_1 = 6 \ \text{V}\$, \$v_2 = 4 \ \text{V}\$, \$v_3 = 10 \ \text{V}\$, \$i_1 = 3 \ \text{A}...
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Why isn't the current through the resistor equal to 1A?

Current through the 1 Ohm resistor came out as 1A, however this is apparently incorrect.
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Use Kirchhoff's laws to find the currents \$I_1\$ , \$I_2\$ and \$I_3\$

I would like to find the currents \$I_1\$ , \$I_2\$ and \$I_3\$. I have the following equations for the currents between the branches \$AB\$ and \$CFB\$ \$I_{AB} = I_{CB} + I_{CFB}\$ \$I_{CFB} = I_1 ...
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What is Vout in this diagram?

I am trying to figure out how I can find Vout in this diagram I am sharing right now. I tried kirchoff but it does not seem helpful or possible to work with and I am assuming Vin is just an arbitrary ...
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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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Consistently assigning electrode nodes in random resistor networks

In the context of random resistor networks, the general question of interest is often "what is the effective resistance between two arbitrarily chosen nodes?" But more specifically about the nodes we ...
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How do we get the negative voltage input value of this Op-Amp?

This is an exercise we did in class about the linear limitations of an Op-Amp, I get how we get the conductance and the Current value. But I don't understand in this KVL how did we get the value of $$...
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Find potential difference between nodes A and B in circuit below

By KVL and KCL Ix = 4A and Iy=Iz=6A The potential difference between A and B = Va - Vb = 6 +8Ix =38V I don't understand how we calculated the potential difference using KVL and KCL
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How do I determine the unknowns for this equation?

Suppose a series RLC circuit in series with a 12 V battery and a switch initially opened. R = 100 Ω, L = 100mH and C = 10uF. L and C are initially discharged. A t=0 the switch is closed. I want to ...
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Solve \$n \times n\$ rectangular grid of resistors for mesh currents

I am modeling a mechanical process by using an electrical analogue. I need to calculate the loop (mesh) currents, then I can see if any mesh current is greater than a predetermined value \$\lambda\$. ...
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What is V in this circuit?

This question on kirchoff's second rule every time I calculate it I get +12V but in my book's answers it's -12V. Could someone solve it and tell me what I'm doing wrong or is the book itself wrong ? I ...
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Problem KCL in PSPICE simulation

I have simulated the following circuit and have trouble with it. Why are the input and output currents are not equal? Is this problem from me or with SPICE?
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Resistor Coefficient Voltage Matrix Doesn't have a Solution

Follow the link to the circuit that I need to solve for all the resistor voltage drops. I have to make 5 linearly independent equations in order to solve for all 5 unknown voltages. Using the loops ...
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Does this circuit follow Kirchhoff's current law?

For the above typical circuit, when the transistor is off many texts show the current directions as shown in pink colour. I also know from basic circuit theory: "The algebraic sum of all currents ...
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Interpretation of Generation and load power at a bus and understanding of slack bus

I was going through the IEEE 14 bus system data from [here] (https://ijireeice.com/wp-content/uploads/2013/03/IJIREEICE2E-a-shkti-Computation-of-final-21.6.14.pdf). I know that there are three type of ...
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How do I find Vo in the circuit?

I1 + I2 = I3 I1 = Vi/Z1 ... Z1 = (1+sCR1)/sC I1= Vi(sC)/(1+sCR1) I2= Vi/R1 I3= -Vo/R1 I1 + I2 = I3 Vi[(sc)/(1+sCR1) + (1/R1)] =-Vo/R1 -Vi[(R1sC)/(1+sCR1) + 1] = Vo How do I change back to time domain?
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How can I solve the following phasor analysis question?

How can I solve part B? Obviously, since the two sources have different frequencies I started off by killing the voltage source (short-circuit) and then tried to apply KCL. My goal was to find the ...
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Double loop, double voltage source circuit analysis problem, with three unknown voltages/currents, using Kirchhoff's laws and Ohm's law

I'm currently studying the textbook Fundamentals of Electric Circuits, 7th edition, by Charles Alexander and Matthew Sadiku. Chapter 2.4 Kirchhoff's Laws has the following practice problem: Find the ...
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How to do mesh analysis when 2 mesh are sharing the same voltage?

I was doing superposition theorem and trying new numericals and then I came across this problem..should I write "9 volts or 9(IsubA-IsubB)" in mesh 1?
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Is SPICE's transient analysis erroneous for converging diodes with 0 current?

Let's say you have 4 voltage sources, set to V1, V2, V3, and V4 with respect to ground feeding the anodes of respective diodes D1, D2, D3 and D4. What is the voltage across each of the diodes? ...
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Effective resistance from a random resistance network

I am trying to calculate the equivalent resistance from a random resistance network formed by carbon nanotubes (CNTs.) I have a MATLAB program where the CNTs are randomly distributed inside a volume. ...
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Analyzing a circuit with 2 voltage sources

This is a problem given to us for homework: This is the first question I've got that has 2 power sources and I'm stuck on calculating the potential difference and current through R3, R4, and R5. I ...
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Trouble understanding a given circuit for an LDR pulse sensor

I'm a second year physics student, part of a group, and we're trying to build a pulse monitor following this guide. This is the schematic I'm having trouble to understand: I have basic knowledge of ...
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How current flows in a circuit as per Kirchhoff's law if the voltage dropped = voltage applied

According to the Kirchhoff's law the voltage drop is always equal to the voltage applied, then how come the current even flows in the last part of the circuit? For example if in a circuit which has a ...
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Current flow in circuit

I do not understand why the direction of I3 is to the right, I am supposed to find Vs which the solution is 36V, my only problem is the direction of current for kirchoff current law, so I would like ...
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Circuit analysis using KVL

But, the answer is different. Given \$i=-8A\$ and \$v_0=48V\$. Can't understand where is my mistake. Please help.
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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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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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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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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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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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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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DRV8889: Unexpected voltage drop at output

I'm getting some unexpected behaviors when it comes to the voltage and current I see at the AOUTx and BOUTx pins. I must be missing something from my calculations from the datasheet. Right now, I'm ...
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Calculate the current

I was practicing for the exam suddenly I found this question the professor solved, but I think whether he or I made a mistake. Part (III) in the image. His calculation is on the image he added the ...
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How to get power in dependent voltage source?

l've made a simple circuit using Thevenin's theorem, and then help me which node to formulate to solve the problem. (I've written Thevenin's theorem, am I writing it correctly?) Also, Vx is a ...
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Potentiometer Working

Let's suppose that \$E \gt V\$. Now, the voltage \$V_b\$ at point \$b\$ will always be \$V\$ and will not depend on \$E\$. Similarly the voltage \$V_A\$ at point \$A\$ is \$V_E\$ which will be ...
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Kirchhoff Voltage Law in a two port network

In a tutorial about h parameters of a two port network, I find the below snippet in the image unable to grasp. According to KVL, the total voltage in a loop is the algebraic sum of the individual ...
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Output Voltage Formula verification of Operational Amplifier circuit

I'm trying to built an op-amp circuit for a PT100 temperature sensor. I've found the following circuit diagram online (from a polish website): And I'm trying to find the formula for the output ...
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How to write inductor ODE equation properly?

I've drawn a following scheme, and now want to write ODE system for describing inner processes, in order to explore it: simulate this circuit – Schematic created using CircuitLab I wrote the ...
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Basic electrical circuit loops

Hi I have a basic electrical circuit and I am trying to make loops. Those things on IMG-2. I just don't understand how are they made. Why are the "one square loops" only in upper squares and not ...
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KVL in the capacitor during transient analysis

I can see that this topic has been discussed many times in this site. But I still can't figure out why I am still not getting my correct equation applying the KVL. Consider a circuit as shown: ...
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Do photodiodes break KVL?

I know what you are thinking, but hear me out. Let's do KVL in this loop: simulate this circuit – Schematic created using CircuitLab We get: $$ -V_{PD}+I(R_s+R_L)-V_1 = 0 $$ Now we solve for ...
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