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Questions tagged [kirchhoffs-laws]

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

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What am I doing wrong? (Basic circuit excercise)

I've tried to solve this circuit and I get that Iy and I5 are 0 A, and this can't be possible since Iy is a current source. What am I doing wrong? *Another question. Lets suppose there was a current ...
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Clamper circuit, how to apply kirchhoff when the diode is turned around?

in this clamper circuit it's easy for me to determine the output waveform: This is how I do it: In the positive half cycle, the diode is forward biased with a drop of 0.7 V, so the positive half ...
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Solving a circuit with Nodal Analysis [closed]

I've been trying to start solving the circuit for a long time now, but I've no idea where to begin, what node should be grounded. Someone please solve this circuit ina detailed manner
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Direction of current flow in resistor networks

We have a simple resistor network \$g\$ with \$5\$ nodes and \$6\$ edges (resistors) as given below: We assume all resistors have the same resistance (say \$1\$ Ohm, so homogeneously distributed ...
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Weird Kirchhoffs laws circuit

See image - I dont have any idea on how to start calculating this circuit using Kirchhoffs laws. There isnt any kind of this circuit anywhere on the web as far as I can see. I would be very thankful ...
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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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Doing KVL on PNP BJT

I'm trying to find the voltage at the emitter and i use the property they give me of the absolute value VBE where in the book its equal to the small AC signal plus the DC VBE ( in this case that small ...
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How do I solve the current of this circuit with a diode?

I am trying to calculate the current of the circuit but I am unable to find the correct answer. I was able to solve the same circuit without the diode witch gave me 2mA. I am unsure of what to do with ...
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72 views

Find the current at the resistor

I've tried to divide current at 8A and then make a Kirchhoff voltage law between the resistor and dependent current source but I still can't solve it.
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Can I apply Kirchoff's law in the open contour in the picture

So is it right if I apply Kirchoff's law : Vcc=I1R1+I2R2+I3Re if I1 is the current that flows in R1 resistor, I2 in R2 and I3 in Re
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If the order of any component is altered in a series circuit, will the total voltage be affected?

I recently posed this question to someone. I always thought that the answer was simply no because of Kirchhoff's voltage law... However, their response was... "no, the voltage is not altered due to ...
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Matlab: Solving homogenous set of linear equations based on Kirchhoff's circuit laws

I have got the following equivalent circuit of a common source amplifier from which I want to determine the expression for the voltage gain A = VD/VG. Because I have pretty much more difficult ...
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61 views

Potential difference between these points

I do not know how to approach this problem or which theory to apply. Could you please help me to find out the potential difference between the points A and B in the circuit given below.
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142 views

As we go around the circuit, the total voltage drop must equal zero

I am studying an advanced mathematics textbook. One of the examples is within the context of an electrical circuit (a series circuit, I think). The example makes the following claim: As we go ...
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72 views

How is voltage divided between two reverse-biased ideal diodes?

Suppose we have two identical ideal diodes (without any resistance or voltage drop). We connect these two diodes in series, in the same direction, and reverse-bias them with voltage V. Now we have two ...
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140 views

Transistor circuit driving me insane

Consider the following circuit: Now I'm asking to impose the base current as zero and $$R_C=452.35 \Omega $$ Now I have a lot of issues with this circuit because I can't find a systematic way to ...
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Can't understand a given answer about a 1st Kirchhoff's law question

I am currently studying the textbook "Lectures about the fundamentals of Electrical Engineering" by Adalbert Prechtl and after finishing the theory about Kirchhoff's law, I tried to solve some basic ...
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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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Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?

In this video, the electrical engineer and youtuber Mehdi Sadaghdar (ElectroBOOM) disagrees with another video from professor Walter Lewin. Basically, professor Lewin shows in an experiment that if ...
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What is the best approach to calculate the transfer function of this RC circuit?

I want to calculate the transfer function of the circuit below. I tried to calculate the equivalent impedance of each block and work my way with voltage dividers until I get to V3, but this method is ...
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Kirchoff law exercise

I need to determine the current across the 4 ohm resistor (name it I1). What I calculated, thought out so far : Current of 2 ohm resistor : I=5V/2ohm=2,5A. I Think this current is flow towards the A ...
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How can I solve for impedances if given RMS currents?

Given a very simple circuit such as this. If I where given the RMS values for the three currents, how could I go about solving R and Xl? (the resistor and inductor in paralell) I know I can not ...
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Calculate the Norton Resistance and Current and the Thevenin Voltage of the following circuit

U=10 V, R=10 ohm I calculated the resistance as such: 1/Rt = 1/R + 1/R <=> Rt = R/2 = 5 ohm To calculate the voltage I did KVL as such: U - 2Ur = 0 <=> Ur = 5V, where Ur is the voltage in the ...
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Calculating the Thevenin Voltage of this circuit

What I did was apply kirchoff's voltage law to the closed network with the 2 resistors and the voltage source to calculate the voltage of the resistors. I got U - 2*Uresistor =0 <=> Uresistor =5V ...
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Transistors, explanation of current gain

At this first picture i have a NPN transistor with Beta=75, 2N222A transistor, both Inputs are 5V. it was very simple to calculate the current that will flow through the LED. as it is simply I1 * Beta ...
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62 views

If we have four grounded nodes in a circuit, can we connect two of them together and forget that those two were grounds?

Refer to the image attached. I personally think the answer is no because it is not necessary for the currents through both the grounded capacitors to be the same in the upper circuit, but that is not ...
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i don't understand the KVL solution to this question?

this is part of the solution of a previous exam and there are some things i don't understand about it 1- why did he assume the value of current at the 12 Ohm resistor to be 0.5A without any ...
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85 views

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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LED's brightness difference in these 2 circuits

I have past exam's problem as follows. Suppose there are circuit A (left image) and B (right image). The question is why LED in circuit A is brighter than in B. The solution states that the Low-level ...
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Is this equation wrong?

I have a trouble in understanding one of the current equation in the following example: https://www.circuitlab.com/textbook/dependent-source-feedback/ To me i3 = (Va - Vb)/R2 which yields: Va - Vb ...
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129 views

Analyzing a constant current source

I'm looking at some old chemistry education literature where a constant current source was proposed (J. Chem. Ed. 1969, 46(9) p613, link). I am trying to better understand the circuit and could use ...
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38 views

Basic KVL question

I'm trying to derive the output resistance of a common-source MOSFET with source degeneration. Are my KVL equations correct? I feel like it's very wrong.
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163 views

Confused about KVL / KCL / ohm's law

I am confused about when to use KVL/KCL or ohm's law to solve the circuit question? I need to compute voltage in point B and point C, every current pass through R1 R2 R3 R4 R1= 100 ohm, R2=300 ...
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127 views

How do you write the system of equations that solve the nodal voltages for this circuit?

I have the circuit below drawn on a piece of paper. I am trying to figure out the unknown nodal voltages x1-x9. Actually, from the circuit we already know x8=9 and x9=0. Here is my thought ...
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Kirchhoff's Law - Finding i in non series/parallel circuit

I am trying to solve this setting up equations to each node. Node A: 10A + i5 = i Node B: i + 4A = i3 Node C: i3 + i2 = i4 Node D: i1 + i4 = i5 I am lost from ...
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Ultra simple circuit (2 Resistor, 1 Voltage, 1 Current): Kirchhoffs Laws don't give the solution; Superposition, but how?

I am doing a course on Coursera "Intro to electronics" as electronics always was my weak point. Now we discuss npn transistors and I have simplified circuit diagram (see below) where I am supposed ...
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65 views

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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367 views

Mesh Current Polarity, Equation Setup

Practicing Mesh Analysis I came across this problem and te answer is really alluding me and I believe is just one polarity that I'm not understanding, the problem is the following... Vs​=10V, R1=...
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45 views

Voltage drop across resistor

To find the potential difference between the points A and B: On applying KVL between A and B, why we do not consider the voltage drop across the 10ohm resistor?
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49 views

Direction of current in a LR circuit

Assume the easiest circuit with a voltage source U(t), a inductor L and a resistor R in series. The voltage source is function of time. We can have a differential equation: $$U=I'L+IR$$ But the ...
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51 views

Trying to calculate Vae by Kirchhoff KCL

I have this circuit. I am trying to calculate the voltage between A and E by using Kirchhoff current law. This is what I did. First I wrote the equation for the left side, starting at A clockwise: ...
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150 views

Simple question: pros and cons of choosing MESH or NODE methods?

My question is about MESH and NODE methods, how I choose to use one over the other? For example if I have this circuit, my professor used the node method, but also a mesh method could be used? Why? ...
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483 views

Using mesh analysis to get the transfer function of electrical system

I am studying the book: Control system engineering for Norman S Nise. I left the college few years ago, and I forgot lots of thing about Kirchhof's laws (Voltage and current). I tried to solve the ...
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59 views

Circuit analysis, simple KVL

I have come across this example problem and can't determine the why behind why this comes out the way it does: So in figure 3.9 part a) they get 4 volts for \$v_{R2}\$, however the negative voltage ...
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104 views

Fundamentals: KVL in this AC circuit doesn't add up

I've got the following circuit: And with it the following meter readings: In the condition RL, the capacitor has a short over top of it and in RC the inductor has a short over top of it. My ...
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55 views

Find Thevenin equivalent voltage - Circuit Analysis

I am trying to understand how to calculate Vth (between the blue Volt meter and the grey volt meter). I have calculated the current correctly using KVL. However, I can't find a way to calculate Vth. ...
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123 views

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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Kirchhoff's law when using an OpAmp

The blue text is mine and the black text is given by my teacher