What is Node voltage: Definition and 61 Discussions

In electric circuits analysis, nodal analysis, node-voltage analysis, or the branch current method is a method of determining the voltage (potential difference) between "nodes" (points where elements or branches connect) in an electrical circuit in terms of the branch currents.
In analyzing a circuit using Kirchhoff's circuit laws, one can either do nodal analysis using Kirchhoff's current law (KCL) or mesh analysis using Kirchhoff's voltage law (KVL). Nodal analysis writes an equation at each electrical node, requiring that the branch currents incident at a node must sum to zero. The branch currents are written in terms of the circuit node voltages. As a consequence, each branch constitutive relation must give current as a function of voltage; an admittance representation. For instance, for a resistor, Ibranch = Vbranch * G, where G (=1/R) is the admittance (conductance) of the resistor.
Nodal analysis is possible when all the circuit elements' branch constitutive relations have an admittance representation. Nodal analysis produces a compact set of equations for the network, which can be solved by hand if small, or can be quickly solved using linear algebra by computer. Because of the compact system of equations, many circuit simulation programs (e.g., SPICE) use nodal analysis as a basis. When elements do not have admittance representations, a more general extension of nodal analysis, modified nodal analysis, can be used.

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  1. Purpleshinyrock

    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...
  2. Purpleshinyrock

    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...
  3. D

    AC - Node Voltage Method for difficult circuit

    Hi! I'm trying to understand and solve this circuit by Node Voltage Method. I have to calculate u(t). In my mind, I don't have any idea if any current should go through Z1 in my calculations. I would be grateful if you could write even equations for this circuit. Is 'a' just a prefix to multiply...
  4. Boltzman Oscillation

    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...
  5. R

    Node Voltage: Where to choose ground?

    Hello, Here's the example I'm looking at now. I am wondering if I swap ground and Node C... will this still be correct? I can see how it's more useful to have ground where it is above, but I'd still like to know if it would work for a swap of C and GND. Here's my work trying this: Does...
  6. R

    Finding the Voltage across a Resistor using the Node Voltage Method

    Homework Statement For the given circuit (see below), find the voltage across resistor 3. Homework Equations n-1 Kirchhoff's Current Laws for n nodes. The Attempt at a Solution Can anyone verify whether my KCL equations are correct? The mixture of source voltages with node voltages may...
  7. V

    PNP Transistor voltage calculation

    For the B) part, I don't get why is it that for calculating voltage between collector an the emitter (Vce) I take into account diode on base (0.7V), whereas for part A) it's ignored? Why is Vce in part A and part B are calculated differently? Why is it that in part A voltage of 0.7V isn't taken...
  8. S

    Find Vx using node voltage method

    is= 1.2 mA i submitted my solution but it was wrong,can someone please explain why? /* i just wanted to check if my solution is correct so i don't lose marks on my homework did i do any mistakes ? if so please explain.*/ my solution:
  9. V

    Circuit with two voltage sources, finding voltage at nodes

    Okay, so why is it that Vc assumed to be 12v - 0.7v (D1), how about contribution from the 9v battery?? Why is this not affecting the voltage at node C? Why Vc isn't 9v - 0.7v (D2) = 8.3v?
  10. Cocoleia

    Is Vb 0V in this Op-Amp circuit?

    Homework Statement I am wondering if in this circuit Vb will be 0V? Homework EquationsThe Attempt at a Solution I have found all the other ones, but I am unsure if Vb will be 0 or not, and if it is then what is the logic behind it?
  11. TheBigDig

    Calculating Node Voltage using Nodal Analysis

    1. Homework Statement The circuit is driven by a voltage source, Vs(t)= 8.2 cos(1.8 t − 0.25 )V . The circuit elements are given as follows. G1= 5 S,G2= 7.6 S,G3=3.8 S (Gi is the conductance of corresponding resistor Ri) L1= 20 H,C1= 5×10−2 F If we select Node 4 as the reference node...
  12. Marcin H

    Engineering Bridge/Ladder Circuit and Node Voltage Method

    Homework Statement Homework Equations Node Voltage Method V=IR The Attempt at a Solution So I have never worked with a bridge/ladder circuit before and I am not sure if I am doing it correctly. My professor never gave us an example of a bridge/ladder so I'm kinda winging it. Anyway can I...
  13. Marcin H

    Node Voltage Method: Find Voltage Across 6A Current Source

    Homework Statement Find the voltage, V, across the 6A current source Homework Equations V=IR Node Voltage Method The Attempt at a Solution Did I set this up correctly to find my voltage?
  14. C

    Node Voltage Current Direction

    Homework Statement Hi all, how do I know how the current direction are through each elements after solving a circuit (finding node voltages w.r.t GND)? I think my understanding in electricity is rather incomplete. For example, I know that current should flow from a higher potential to a lower...
  15. D

    Determine current and voltage using Node Voltage method

    [Mod note: Post moved to new thread, so template not included] Hello there again! I started working on the second problem but I think I am doing it wrong so I thought I would post the first step and do this one step at a time to see where the mistake was. So the task is to determine UR3 and...
  16. jdawg

    Node Voltage Analysis for Finding V1 in a Circuit

    Homework Statement Find V1. I attached a picture for the circuit. Homework EquationsThe Attempt at a Solution This is what I did (Refer to Fig. 1): -2A + (V1)/(50) +(V1-45)/(1) = 0 But when I looked at the solution my professor posted this is what he did (Redrew Fig.1 as Fig.2): -2A +...
  17. jdawg

    Solve Node Voltage Analysis: I1, I2, I3 Values

    Homework Statement Use node voltage analysis to determine values for I1, I2, and I3. If a current has a negative value, then the reference direction chosen was incorrect and the current is positive in the opposite direction. I attached a picture of the circuit. The things in blue (current ix...
  18. thegreengineer

    Nodal analysis, choosing number of nodes confusion

    Good evening people. Recently I started taking the "electric network analysis" course in my school. We already saw the mesh analysis method for solving circuits. Now we are seeing the node analysis method. I understand that the first step for this method is finding the number of nodes (and one...
  19. STEMucator

    How to Determine Correct Node Voltages in NMOS Circuit Analysis?

    Homework Statement Find the labelled node voltages. Assume ##k_n = 0.5 \frac{mA}{V^2}## and ##V_{tn} = 0.8V##. Neglect channel length modulation ##(\lambda = 0)##. Homework EquationsThe Attempt at a Solution f) For this problem, I see ##V_D = V_G \Rightarrow V_G - V_D = 0V \Rightarrow...
  20. T

    Solve Node Voltage Analysis: All G=1S, 3A Current Source

    Homework Statement Determine the three node voltages, va, vb, and vc, when all the conductance's are equal to 1S Circuit Diagram: The labels are a bit cut off, hope you guys can see it. The current source parallel with G2 is 3A Homework EquationsThe Attempt at a Solution [/B] I think their...
  21. B

    Node voltage with dependent voltage source

    Homework Statement http://i62.tinypic.com/245fwxu.jpg[/B]Homework Equations & Attempt to solve [/B] http://i62.tinypic.com/142v6mv.jpg Bottom: A Top left: B Top Right: C(1/100 + 1/5 + 1/25)VB - (1/25)VC + 6.25I = 450 mA (20.8)VB - 0.04 VC + 6.25I = .450 A VC = 45 + 6.25I I know I'm doing...
  22. C

    Use the Node Voltage method to solve

    Homework Statement From the above circuit find VCB and VDG Know Data: VE = 0 (ground) Homework Equations KCL and Ohm's Law are used in Node Voltage Method. The Attempt at a Solution I decided I would determine the node voltages then work out VCB and VDG afterwards. 1. KCL and Ohm's law at...
  23. O

    Node Voltage Method: Solve for v0 in Circuit

    Homework Statement Use the node-voltage method to find v0 in the circuit below. Homework Equations i1+i2+...in=0 i=v/R The Attempt at a Solution So I set my reference node to the top of the middle line(above 25Ω) Equation... 24V/(20+80)Ω+v0/25+.004A=0 Now I can solve for...
  24. C

    Engineering Circuit Analysis- Node Voltage Problem

    In the attached picture, I have the problem and the equations I've come up with to solve for the requested variables. I have found seven equations for the seven unknowns, however, after plugging them into a calculator my answer is wrong. Which equation(s) is/are wrong, and why? Relevant...
  25. Y

    Equivalent resistance, using node voltage analysis

    Homework Statement (I added in the R values for reference) Homework Equations GV=I KCL The Attempt at a Solution I am not concerned with the MATLAB portion of the problem, only the setup. I think what the problem wants me to do is: 1) connect a 1A test current from the...
  26. U

    Engineering Node Voltage Circuit Analysis: Solving for V1, V2, and V3

    Hi, I am given a node voltage problem to find V1, V2, and V3 from this image below. http://puu.sh/77Sg3.png (v1+15)/20 + (v1-v2)/25 + (v3-v2)/50 + (v3 - 10)/10 = 0 18V1 - 12V2 + 24V3 = 50 V2: (v2-v1)/25 + v2/40 + (v2-v3)/50 = 0 17V2 - 8V1 - 4V3 = 0 15 = V3 - V1 Am I in...
  27. K

    Node Voltage Analysis: Solving VA & VB

    I am having a hard time trying to determine the voltage at VA and VB. I know that VC = VD = 10V. At first I thought this would be a simple setup, but I'm unsure about how to set up an equation for VA considering that there is a resistor and a voltage source between it and the reference node...
  28. S

    Engineering Finding Vo Using Node Voltage Method: A Calculator Puzzle

    Homework Statement Find the voltage Vo using node voltage method specifically.Homework Equations The Attempt at a Solution I am able to get the correct answer when finding the equivalent impedance, then determining the current, and then finding the voltage at the first node V1 by subtrating...
  29. T

    Node Voltage Analysis: Solve Unknowns & Get Help Now!

    Hey PF I need your help...again! Homework Statement Use Node Voltage Analysis to solve the unknowns in thishttps://dl.dropboxusercontent.com/u/53341615/Question.png The Attempt at a Solution Im quite confused and have had many attempts...
  30. C

    KVL Node Voltage: Positive vs Negative Assumption in Homework Solution

    Homework Statement Homework Equations ƩCurrent(in) = ƩCurrent(out) The Attempt at a Solution ----In situations like that, my book takes the node to be a positive voltage when the voltage source is connected like above. For some reason my professor takes it to be negative, is this why my...
  31. G

    Circuits Question Node Voltage Method

    Homework Statement I'm having problems finding the power. I should my work to get the node voltages. Apparently they are correct. I showed how I got to those answers as well just in case they were wrong but I don't think they are. http://img547.imageshack.us/img547/8812/capturebu.png...
  32. T

    Node Voltage Analysis Questions

    Hopefully it's ok if I post two questions QUESTION 1 Homework Statement Homework Equations Node voltage analysis method The Attempt at a Solution First of all is this circuit equivalent? (combining the 10 ohm and 4 ohm in parallel, and extending the ends of the protruding 10...
  33. P

    Node Voltage (is my answer correct )

    http://www.flickr.com/photos/84781786@N03/7822251544/ Find the node VOLTAGE for V1,V2,V3,V4 Homework Equations KVLThe Attempt at a Solution V1 = 6V V4= 16V V2= V2/1.5k - 6/1.5k + V2/ 1k + V2/3.3k - V3/3.3k 6/1500 = V2/5.8k - V3/3.3k V3 = V3/2.2k + V3 / 4.7k + V3/3.3k - V2/3.3k - 16/2200...
  34. C

    Sloving a depentant voltage source problem using node voltage

    Hi everyone, I currently stumped in the process of approaching a dependent voltage source problem using node voltages. Attached is the circuit. What I know: the Node north of the 60V supply with also be 60V there are four nodes, two when supernodes are used What I'm confused...
  35. S

    How to Find Node Voltages Using the Node Voltage Method in Multisim?

    i solved this problem which asks to find the node voltages ,, http://im12.gulfup.com/2012-02-19/1329666252272.png and here is my sol : http://im12.gulfup.com/2012-02-19/1329666252271.jpg and finally i found that : v1 = 226.25 volt v2 = 20.92 volt v3 = -63.07 volt v4 =...
  36. B

    I don't understand why the node voltage here is zero(this is for circuits class)

    My teacher was going over a thevenin and norton circuit and i understand the thevenin and norton part of it, but the part that confused me was when he did the node voltage at the 2 circled nodes to find Ix. I understand why the bottom node would be zero because it is the reference node but why...
  37. C

    Problem with Node Voltage Method

    1. Find the power delivered by the 5V Voltage source in the network of Fig. This is my attept at solution: At node 1 V1...assuming current leaving V1: KCL equation: -1A+1A+[(V1-5)/3]+[(V1-(V2-10))/2]=0 At node 2 V2...assuming current leaving V2: KCL equation: -2A-1A+[V2-(V1+10)]=0...
  38. F

    Node voltage Analysis with voltage controlled voltage source

    Homework Statement Here is the circuit http://i.imgur.com/Xn2mc.jpg The Attempt at a Solution I've tried it a few ways, but the one I'm going for at the moment is this Node 1: (v1-v2)/10 + (v1-v3)/15 + v1 /5 = 1 Node 2: (v2-v1)/10 + (v2-v3)/10 + v2 / 5 = 2 Node 3: 2Vx where Vx = (v2...
  39. O

    Node Voltage Analysis: Solve for V1, V2, V3 and V4

    Homework Statement Solve for V1, V2, V3 and V4 (in decimals) using node voltage analysis method for the following: Homework Equations: Node Voltage Analysis The Attempt at a Solution: For Node #1: V_{1} = 6 V For Node #4: V_{4} = 16 V For Node #2...
  40. S

    Node voltage w/ voltage source

    This question has been driving me crazy because i am unsure when i am able to apply voltage division to portions of a circuit i try to analyze. I know the potiential difference across a voltage source always needs to be equal to the value of the voltage source but, if the branch coming out of...
  41. C

    Can someone help me with node voltage analysis?

    Homework Statement In the figure, use the node voltage method to find the voltage at point A with respect to ground. Sorry for the crudely drawn picture.Homework Equations Node voltage analysisThe Attempt at a Solution First I added R3 and R4. Then I tried to find the current equations...
  42. Q

    How Do I Correctly Apply Node Voltage Analysis?

    Homework Statement Determine the node voltages, Va and Vb of this circuit: http://img198.imageshack.us/i/circuitx.jpg/ Homework Equations The Attempt at a Solution Node a: 3 V - Va/4 + (Va - Vb)/2 = 0 3 - Va/4 + 2Va/4 - 2Vb/4 = 0 3 + Va/4 - 2Vb/4 =...
  43. N

    Use node voltage method to solve i2 vbe and vce

    I have attached the problem and the worked out solution can a few people go over it and post if it's right and if not what is wrong with it. Using node voltage method
  44. L

    Node voltage current direction?

    When doing node voltage analysis with KCL. (eg sum of currents into each node = 0). Do we assume all the currents are going INTO the node, or out of the node. maybe it's just my math but, assuming different things gives different answers. The textbook (hambley's) says that it's fine to select...
  45. jegues

    Node Voltage Question: Solve My Attempt!

    Homework Statement See Figure Homework Equations \Sigma i_{out} = \Sigma i_{in} The Attempt at a Solution My attempt is in the figure. Is this is what they are asking for? Or do I need to add something else? Is what I have correct? Thanks again!
  46. B

    How Does a Star's Mass Loss Affect Satellite Orbit Distances?

    Homework Statement A satellite is in circular orbit of radius R about a star of mass M . The star suddenly undergoes an explosion in which one percent of its mass is blown spherically symmetrically to a large distance. What are the new nearest and furthest distances of the satellite’s...
  47. James889

    How to Correctly Apply KVL for Node Voltage Analysis?

    Hi, I have this circuit which i am trying to write KVL equations for, but i just can't seem to get it right... [PLAIN]http://img146.imageshack.us/img146/3374/upg255.png The equations i have written so far are: For v1: \frac{v_1-v_2}{5} +\frac{v1}{10} +1 = 0 For v2: \frac{v_2-v_1}{5} -...
  48. E

    Node Voltage analysis- electrical engineering

    http://i39.tinypic.com/28akmfk.jpg Ultimately, I am trying to find power dissipated by each resistor. I already applied node voltage analysis to the circuit. The picture shows the diagram of the problem and my attempted solution/ equations I came up with. In the diagram, I labeled...
  49. 3

    Solving Node Voltage: Va = Vb x R1/(R1+R0)

    Homework Statement Find the node voltage Homework Equations Va = Vb x R1/(R1+R0) The Attempt at a Solution I didnt have the original picture of the question but this example is exactly same as the question that i had to solve. but I don't understand this thing from the first...
  50. W

    PSC, current and Node Voltage Analysis

    First off, I apologize if this belongs under homework help. It’s kind of a grey area I suppose... Anyway, I just finished my linear circuits midterm. One of the questions on the midterm had a circuit we needed to solve using node analysis. That’s not the question, though. I’ve crudely redrawn...
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