# What is Kvl: Definition and 92 Discussions

Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirchhoff. This generalized the work of Georg Ohm and preceded the work of James Clerk Maxwell. Widely used in electrical engineering, they are also called Kirchhoff's rules or simply Kirchhoff's laws. These laws can be applied in time and frequency domains and form the basis for network analysis.
Both of Kirchhoff's laws can be understood as corollaries of Maxwell's equations in the low-frequency limit. They are accurate for DC circuits, and for AC circuits at frequencies where the wavelengths of electromagnetic radiation are very large compared to the circuits.

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1. ### Engineering Derive the governing equation for the voltage Vc across the capacitor

I was thinking about doing KVL around the circuit at the right but I noticed when the switch opens, the current through the circuit at the right is not the same throughout -5 + Ic*2*1-^3 + Ic*10^3 = -Vc Ic is not the same around the right circuit so I am stuck....
2. ### A confusing question on capacitors and voltages across them

In my opinion, the voltage across the C1 should be 9V as the potential on the side of the positive plate of the capacitor should be (15-6)V and on the other be 0V. Similarly the potential across C2 should be (7-0)V. Here I'm basically assuming that the voltage at the negative terminals of the...
3. ### Engineering Help finding this node voltage

I am given that all the BJTs are the same. First of all, when finding node voltages like Vref should I make the node voltage a voltage source first and then do circuit analysis? If so then I would use KVL but that does not give me Vref = 2Vbe. I do know that Vref = Vb1 = Vb2. What am I doing...
4. ### Engineering Dependent source problem using KVL

Hi all, I was trying to solve this but I'm stuck as you can see in my notes below: Using simulator the I1=3.125 A | I2=-1,857 A | I3=4,375 A and Power of the dependent current source = -46.875 W Any idea, what could be wrong ?Thanks.
5. ### Calculating Vo in an AC Circuit Using Superposition Theorem

This is the circuit: I try with KVL: But the given answer is 6.66L33.67 Volts. So, I'm confused, any suggestions ?
6. ### Engineering How can Kirchhoff's Laws be used to solve for current in a circuit?

I've been trying to use KVL/KCL here but I can't get any. The only thing I accomplished is R6 has 0V, 0A (KVL with its loop). All the other ones I can't get any? Thanks
7. ### How to handle KVL limitations?

Hi, I was reading KVL and KCL and I read that KVL cannot be applicable to all the situations specially when :- " KVL is applicable on the assumption that there is no fluctuating magnetic field linking the closed loop. While, in presence of changing magnetic field in a High Frequency but short...
8. ### MOSFET KVL Confusion: Finding Vg | Homework Solutions

Homework Statement Homework EquationsThe Attempt at a Solution My first attempt was to figure out what region the PMOS is operating in so that I could decide what equation to use - so I tried to find Vgs. Vgs = Vg - Vs. Vs is of course just Vdd but for Vg I did a KVL loop as below: My...
9. ### Engineering KVL and sensitivity of a simple circuit

Homework Statement Homework Equations The Attempt at a Solution Note to self - simple diode concept: http://www.cs.tut.fi/kurssit/TLT-8016/Chapter3.pdf#page=5 Unsure about this KVL (above). For the last sensitivity part, equations be falling out of the sky...
10. ### Engineering Fundamentals of Electric Circuits - Sadiku Question on KVL

Hi, this is my first time posting, I'm glad there is a space like this where we can share our doubts and hopefully get some help from other students. As you can see on the image above, there's a KVL applied to the circuit in practice problem 2.6, but my question is the following: On equation...
11. ### Thevenin Equivalence: Is my workings correct?

Homework Statement https://imgur.com/a/XySpV (If above image can't be seen.) Homework Equations KCL/KCL Rth=Vth/I The Attempt at a Solution Included in Screenshot. What I did was Open-Circuited the Load and use Nodal Analysis to find Voc Then, I shortcircuited the Load to find...
12. ### How do I solve 2 simultaneous equations using KVL?

« thread moved from technical forum; so template is absent » So I'm trying to get a better understanding of KVL by looking up practice problem and I'm having some difficulties. I'm attempting to do this problem my first step is to get an equation for Ia (32v-10ia+8ib = 0) an Ib (12ib+20v-8ia =...
13. ### Engineering KVL and finding circuit currents

Homework Statement The diagram shown below shows a bi-directional opto coupler input interface circuit. When a supply voltage of 20 V is applied the LED carries a current and 2 V is dropped across it. Calculate the value of the LED current and the value of current through the 3 kΩ resistance...
14. ### Confusion about how KCL and KVL are used for diode circuits

Homework Statement This is just one of the example problems in my book which is already solved for me, but I don't really understand their solution which I'll post here: They start out with assuming Vin is very negative, which makes D1 turn on and makes Vout=VD,on+Vin. THen they solve for...
15. ### How does KVL work in transformers?

I have studied ideal transformers (transfer 100% of energy) and that the power loss in the secondary coil is I^2*R.. Then I asked myself, why can't we use these equivalent formulas for power (IV and V^2/R)?? I tried to use them but they gave me different values for power loss I searched for an...
16. ### Use KCL and KVL to find the power supplied by the two ideal sources

Homework Statement The Question wants to find the Voltage Across The Current Source 2A and 5A Homework Equations KVL KCL Ohm's Law The Attempt at a Solution I tried to Using KVL and KCL for all Closed paths and node but I just Couldn't Figure how to relate them to find the voltage across the...
17. ### Use KVL to determine values of branch currents

Homework Statement Homework Equations KVL: At any instant in a closed loop the algebraic sum of the e.m.f's acting round the loop is equal to the algebraic sum of the p.d's round the loop. The Attempt at a Solution 3.1 R1 = BROWN, RED, BLACK, NONE R2 = BROWN, GREY, BROWN, SILVER R3 =...
18. ### Why are these capacitor voltages opposite polarity?

Homework Statement imgur link: http://i.imgur.com/JETj0Cq.png Homework Equations V_L = L\frac{dI_1}{dt} V_L + V_1 + V_2 + V_{R1} = 0 The Attempt at a Solution [/B] Just using basic KVL, shouldn't V_L = -V_2 - V_1 - V_{R1} and so therefore we should get \frac{dI_1}{dt} = \frac{-V_2 -...
19. ### Engineering Solving for i and v_x: A Homework Challenge

Homework Statement Find i and v_x Given answer: 2. Homework Equations 3. The Attempt at a Solution I have attempted the problem in two different manners, and I consistently reach a different answer. I would appreciate if someone would be willing to take the time to attempt the problem and...
20. ### Solve KVL for R and e: 3.2 Ohms, 0 Volts

Homework Statement The question wants to find R and e (epsilon), I found R to be 3.2 ohms but epsilon is 0 volts, which is very weird. original question is attached.[/B] [PLAIN]http:// Homework EquationsThe Attempt at a Solution I also assumed infinite resistance for voltmeter and zero...
21. ### Engineering KVL for a RLC circuit given current direction and polarity o

Homework Statement KVL for a RLC circuit given current direction and polarity of a resistor? Here is the diagram of the circuit: Homework Equations KVL Sum of voltages equal zero The Attempt at a Solution I am actually looking for the voltage across the inductor (VL), so I decided the...
22. ### Engineering Analysing a 3-Loop RLC Circuit and Finding State Equations

Homework Statement Obtain the state equations in Matrix form for the two-input and one-output circuit shown in the figure below where the output is i_2. Homework Equations Ohm's Law, KVL, KCL The Attempt at a Solution Currents i1, i2, i3 assumed clockwise. Is there a better assumption I...
23. ### Engineering EE Solving a circuit using KCL and KVL

Homework Statement Find V0 and i0. Homework Equations Total current at each node is = 0. Total voltage around each loop is = 0. The Attempt at a Solution I can't seem to be able to analyze this circuit. That i0/4 is really messing me up. I am unsure how to apply both KCL and KVL on this...
24. ### Engineering Given RLC circuit to find V over load & other complications

Homework Statement In my Intro to EE class we have a homework assignment with the following problem: I think I finished part a but want to make sure that I am doing the problem correctly before I move on to the next part. Homework EquationsThe Attempt at a Solution
25. ### Understanding KVL Loop in BJT Biasing and Calculating Ve

Please help how Ve is calculated what i think is that it should be: -Ve=-Vee+IeRe; How Ve is taken positive please someone draw equivalent circuit for same
26. ### Engineering Solving a Circuit with Nodal Analysis

Homework Statement I'm in a lab and we have this circuit & question as part of the pre-lab The Attempt at a Solution I began trying to use nodal analysis to get Va & Vb & to then use Vab to get the voltage and then the current but after doing what you can see above, I stopped because I...
27. ### KCL Nodal Analysis & Power to Resistor (Need help)

Homework Statement Here is the homework problem I was given: The Attempt at a Solution Above is the work that I began, however, I have an overwhelming feeling that I am incorrect and also I don't know how to continue to the next part/parts. Would someone please help me? Thank you H
28. ### Solving KVL: Voltage Across All Elements

Homework Statement Determine the voltage across all elements Homework Equations i=v/r v1+v2+v3+..=0 The Attempt at a Solution I'm not sure which of the nodes I should use to take my KVL from. The a and b are labeled, but should I combine the set of 2-6-6 resistors and label that as an...
29. ### Engineering Thevenin's equvalent circuit of the network?

Homework Statement thevenin's equvalent circuit of the network Homework Equations thevenin's voltage thevenin's impedance The Attempt at a Solution using nodal analysis i tried to find thevenin voltage but the dependent source and the dependent variable troubling me!
30. ### How to find the voltage 'v' in the given network?

Homework Statement Homework Equations [/B]The Attempt at a Solution
31. ### Find current using KVL (with dependent source)

Homework Statement Homework Equations V = IR Kirchoff's Voltage Law The Attempt at a Solution [/B] Top loop - a Bottom right - b Bottom left - c Ix = x KVL: top: a(6000) + (a-b)(2000) + 5x - 10=0 bottom right: -5x + (b-a)(2000) + b(3000) + (b-c)(4000) = 0 bottom left ...
32. ### Applying KVL: Understanding the Process and Confusions

hello what is the process to apply KVL exactly? we know nothing in a loop, apart from that it consists of 2 batteries with known polarity and 2 resistors. what do we do? we assign arbitrarily the currents to each of the branches that compose the loop? and then we assign polarities to the...
33. ### Mesh Analysis KVL: Homework Solutions

Homework Statement Homework EquationsThe Attempt at a Solution I'm not getting the correct answers, this is what I tried Loop 1: 150 - 14*i1 - 6(i1+i2) = 0 Loop 2: -24 + 3*i3 = 0 Therefore i3 = 8A 7A = i2 + i3 Therefore i2 = 7-8 = -1A Plugging that in equation 1, I get...
34. ### Multiple Power Source Circuit Analysis

Homework Statement Compute all the currents labeled using the mesh loop method. Homework Equations Parallel Resistors 1/Rt=1/R1+1/R2...+1/Ri Series Resistors R1+R2...+Ri The Attempt at a Solution My attempt at the kvl and kcl analysis, I think I did this wrong because I can't solve for...
35. ### Number of KCL and KVL equations for branch-current method

Homework Statement Find ix and Valpha [/B] Homework Equations KCL KVL The Attempt at a Solution [/B]How do I determine the number of KCL and KVL equations? In this problem I am solving, there are 6 unknowns so I need 6 equations. I can write 4 independent KCL equations, 1 KVL at loop 1(to...
36. ### Help Finding Transfer Function Vo/Vs

Homework Statement Find ##a)\ H(s)=\frac{V_o}{V_s}## of the filter in the circuit below. ##b)\ ##The center frequency ##\omega_0## ##c)\ ##The band-width B Correct answers: ##a)\ H(s)=\frac{6s}{12s^2+11s+1}## ##b)\ \omega_0=0.28\frac{rad}{s}## ##c)\ B=0.71\frac{rad}{s}##...
37. ### Engineering How do I find the current in this circuit?

< Moderator Note -- thread moved from the EE forum to the Homework Help forums > Please view the attached. The answers are: i1 0.1429 i2 0.4286 i3 0.2857 So how do I work this out? I assume you use kirchhoffs current law, can someone show me the step? Thanks :)
38. ### KVL Analysis for Solving Vx: Why Can We Ignore the 6 Amp Source?

the question is to solve Vx. chegg did a kvl in the middle mesh and it turned out to be -2+Vx+8=0, i was wondering why they just ignored the 6 amp source in the kvl. i understand no voltage can be dropped across an ideal current source so why can we just skip over the 6 amp source and go to the...
39. ### Independent Current Source In Series With Resistor

Homework Statement Write the KVL Equation for the outer loop Homework EquationsThe Attempt at a Solution The question above is a sample I have made for such a condition. The goal is not to find the value, but only write the correct equation. If an independent current source is connected in...
40. ### Finding Unknown Currents in a Two-battery Complex Circuit

Homework Statement Look at the circuit given in figure 1. Solve for the three currents, I1,I2,I3. Homework Equations KVL: Sum of voltages in a closed loop equals zero KCL: Sum of currents entering a junction equals the sum of currents exiting a junction Ohm's Law: V=IR NOTE: Nodal analysis...
41. ### Solve KVL: Find V1, V2 Using Voltage Divider Rule

Homework Statement Use voltage divider rule and KVL to find V1 and V2 Homework Equations KVL, v1+v2+..=0 V0*r1/(r2+r1)=V The Attempt at a Solution So I know how to use the voltage divider rule, my question is about the KVL of the loop below. I'm wondering about the 8 V source inside of the...
42. ### Solve KVL and KCL for V0: Find Voltage Using Kirchhoff's Laws

Homework Statement Use Kirchhoff's voltage and current laws to find the voltage V0Homework Equations KVL: ƩV=0 KCL: iin=iout The Attempt at a Solution http://s2.postimg.org/6b2013cbt/001.jpg If you guys want the original circuit diagram, i'll post it. Note: The current flowing through i2...
43. ### Help with Circuits problem (KVL, KCL)

Homework Statement Find v. A value for R is not needed. Circuit is attached. Homework Equations KVL, KCLThe Attempt at a Solution I have no idea where to begin with this one. I found an answer using source transformations by transforming the 4A current source into a 12V voltage source in...
44. ### KVL loop: Example wrong, or did I misunderstand?

In my circuit analysis textbook, there is an example problem using a KVL loop. Though it seems relatively simple, I cannot understand the answer. the loop consists of 3 voltages: -8, 12, and the unknown, Vr2. The polarities (clockwise) around the loop are respectively +,-,+. The answer...
45. ### How Do You Solve a Basic KVL Circuit Problem?

http://imageshack.us/a/img585/9687/kvlf.jpg the work i did on that sheet is completely wrong. I know that Ic = Ia + Ib but can someone help me set up the equations for the two loops please! I can't seem to figure it out and its frustrating me! the answer is supposed to be Ic = (RbE1...
46. ### Assigning Polarities and using them in KVL equation, circuits

I am having trouble understanding how to assign polarities to voltage when it goes through components of a circuit and how those polarities determine the sign of the quantities I put in the KVL equation. Attached is a picture of a circuit. The points where polarity matters are labeled 1-14. I am...
47. ### KVL Solution for Loop A: V1-R1*I1-R2*(I1-I2)=0 vs. V1=R1*I1+R2*(I1-I2)

I attached the circuit. This is the solution that was posted on my course's website. I do not think it's right, but I want to make sure to avoid making myself look dumb. Around loop A, KVL should be: V1-R1*I1-R2*(I1-I2)=0 V1=R1*I1+R2*(I1-I2) This would be answer c. Their answer is e. Is the...
48. ### Can you explain Euler's Equation and KVL in engineering?

In one of my engineering classes we discussed these two topics and I have two questions about this stuff. First question is how does euler's equation work exactly.. e^{j\varphi}=cos\varphi+jsin\varphi Second question is how do you solve this: V_{M}cos\omega t=Ri(t)+L\frac{di(t)}{dt}...
49. ### Engineering Circuit Analysis using KVL and KCL

Homework Statement All variables are given by the circuit unless otherwise stated a) Derive an expression for the ratio (Vo/Vs) Homework Equations KCL and KVL equations The Attempt at a Solution Rs1=2.55kΩ -Vs+ .05Vo +(2.5kΩ/2.55kΩ)Vp = 0 where, Vs = .05Vo +...
50. ### Engineering Solving for elements on a circuit using KCL and KVL

Homework Statement calculate the voltages and currents for each element in the circuit? the resistances are as follows R1 = 1 KΩ R2 = 2.4 KΩ R3 = 1.2 KΩ R4 = 1 KΩ R5 = 1.2 KΩ. Vs= 6V Homework Equations Is - I1 = 0 I1 - I2 - I3 = 0 I3 - I4 = 0 I2 + I4 - I5 = 0 -Vs +V1 +V2 +V5 = 0...