Skip to main content
8 votes
Accepted

How to find the nodal voltage when there is a voltage source across two nodes?

I'd just rearrange the diagram and use source-splitting techniques: - From left to right, it's the same circuit but, breaking it down step by step is easier to analyse. Each step saves maths and is a ...
Andy aka's user avatar
  • 463k
8 votes

Can't find error in nodal analysis

I found out the drop voltage at \$R\$ which is -34. But the solutions say it is -28V. I can't find what did wrong. $$\color{red}{\text{Neither answer is correct }}$$ Think about it: How can the ...
Andy aka's user avatar
  • 463k
7 votes
Accepted

LTSpice outputting the incorrect voltage reading?

Make sure the direction of the current for F1 is oriented the way you want it. LTSpice follows the "passive sign convention" -- namely, the positive current direction through a current or ...
ErikR's user avatar
  • 5,007
6 votes
Accepted

How can you tell what is the net direction of current flow when there are two opposing sources?

Redraw Schematics First Often, it helps a great deal to redraw a schematic. Not always. But sometimes the manual process of it helps you find an insight or two or, at least, develops a feel for things ...
jonk's user avatar
  • 78.3k
6 votes
Accepted

RC Circuit Analysis Direction Changes Formula

The basic constitutive equation for a capacitor is based on these assumed polarities, The equation being, $$i(t)=C\frac{dv}{dt}$$ If you want to define your current as leaving the capacitor then you ...
relayman357's user avatar
  • 3,497
6 votes
Accepted

Strange Nodal Analysis

Your mistake is again the current direction. For \$V_1\$ node you have wrote: $$+12A + \frac{V_1 - V_2}{2\Omega}....= 0$$ As we can see from a circuit diagram the \$12A\$ current is entering the node(...
G36's user avatar
  • 14.9k
6 votes

Nodal Analysis - Kirchoffs Current Law

Preface note: I originally used \$3\:\text{A}\$ as the current source. But I mis-read the problem, as stated. They specify, on the schematic, that the out-flowing current source value is \$-3\:\text{A}...
jonk's user avatar
  • 78.3k
6 votes

How to find V1 and V2 using Nodal Analysis?

To help you identify the nodes in the circuit: If the label V1 had been written next to the dependent source 4Ix at the top(i.e., anywhere on the blue area), it would still be equal to VY because ...
Syed's user avatar
  • 1,149
6 votes

Determine Thevenin's equivalent circuit

Step by step. Don't need text but rules say 30 char.
stretch's user avatar
  • 467
6 votes
Accepted

How does Kirchoff's current law work for sinusoidal voltage sources?

Polarity is not a problem for Kirchhoff's laws. You don't have to change the polarity in the equations - if the actual polarity is different from what you drew, the calculation will say it's a ...
Stack Exchange Supports Israel's user avatar
6 votes

How can same points have different current?

Aren't B and D the same point and shouldn't it actually be (B and B)? If you were analysing voltages then yes, B and D are the same node on the circuit. In this case, however, we're looking at ...
Transistor's user avatar
  • 177k
6 votes

Nodal analysis: negative answers vs book's positive solutions

+1 from me for showing your efforts. It's easily enough to earn a moments response. You can check your own work. I'll just dash out mine for comparison. I disagree with you on 3.9 and agree with the ...
periblepsis's user avatar
  • 10.4k
6 votes

Why does this op-amp circuit show current flowing like that?

is there any reason why it shows current flowing from the negative side of the bottom battery into the op-amp or why its showing current flowing from the positive end of top battery into the op-amp? ...
The Photon's user avatar
  • 131k
5 votes
Accepted

What is the op-amp output voltage for a voltage-controlled current source?

You need the MOSFET characteristics. For example, the IRF540 has the following typical characteristics: So, for example, if your current is 10A the typical Vgs is about 4.75V. You need to add that to ...
Spehro Pefhany's user avatar
5 votes

Where have I gone wrong with this nodal analysis calculation?

Suggestions The first thing I do before attempting to analyze a circuit is to redraw that circuit. The process of just doing it helps me think and gather up a few details that I may not notice so ...
jonk's user avatar
  • 78.3k
5 votes

Determine Thevenin's equivalent circuit

Can anyone tell me what the right answer is/ where I have gone wrong. Here's where your error is: -
Andy aka's user avatar
  • 463k
5 votes

Can't find error in nodal analysis

Your equations ignore the current through R. You can't do that. If you don't believe this, think about what happens when R is 0. For example, your node1 is missing the term \$ \frac{+v_2 - v_1}{R}\$ ...
Scott Seidman's user avatar
5 votes
Accepted

Circuit analysis: connecting positive terminal of battery to reference node

Direct answer I'll write more, later. But first.... There's nothing specifically wrong about connecting the positive terminal of a DC voltage supply (battery or mains-powered) to a 'ground'. A ground ...
jonk's user avatar
  • 78.3k
5 votes

Conditions for a resistive circuit to have a solution

and you don't put two current sources in series or two voltage sources in parallel This condition should be rephrased as: "the circuit does not contain a zero-impedance loop with one or more ...
bobflux's user avatar
  • 79.2k
5 votes

How to solve for \$i\$ using superposition?

First off, redraw the schematic. In fact, you should get into the practice of redrawing every schematic. Even those that already look good. Just do it. And do it every time. The practice is worth its ...
periblepsis's user avatar
  • 10.4k
4 votes

Nodal analysis -> transfer function -> step response

Nodal analysis is based on Kirchoff's Current Laws (KCL), meaning that the sum of all currents will need to sum up to exactly \$0\$. The issue in your equations is related to the fact that outputs of ...
Sven B's user avatar
  • 5,217
4 votes

Dependent voltage/current sources

A voltage/current depending source in real life needs to be built from actual electronic components. Usually made from operational amplifiers or transistors. They vary a bit from the ideal voltage/...
Voltage Spike's user avatar
  • 84.2k
4 votes
Accepted

How to use nodal or mesh analysis with a current source?

My problem here is how current source works. The beauty of source transformation If I redrew your original circuit like this: - Would you find it easier to solve? Would you know what to do next to ...
Andy aka's user avatar
  • 463k
4 votes
Accepted

Node voltages using a combination of voltage and current sources

The first thing I do before attempting to analyze a circuit is to redraw that circuit. The process of just doing it helps me think and gather up a few details that I may not notice so easily, just ...
jonk's user avatar
  • 78.3k
4 votes

What is the op-amp output voltage for a voltage-controlled current source?

Could you please help explain/show how I’d be able to find the voltage at node A? voltage at A is whatever it takes to make Q1 turn on enough so that the voltage across the shunt (Ishunt *Rshunt) is ...
Math Keeps Me Busy's user avatar
4 votes

Determine Thevenin's equivalent circuit

You understood that you considered a series connection of the resistors rather than a parallel connection for \$R_{th}\$. When you have a resistance across measurement terminals - your 2-ohm ...
Verbal Kint's user avatar
  • 22.7k
4 votes

Why do I read 20 microamperes instead of 5?

Just looking at the schematic, the collector current will be a bit less than 2mA before correcting for drop across Rb. If that transistor is a 2N2222A hFE should be between 50 and 300 so base current ...
Spehro Pefhany's user avatar
4 votes
Accepted

How do I solve the circuit below using nodal analysis?

Feel free to ask questions, if you have them. But what follows is nodal analysis, not mesh. Assign \$0\:\text{V}\$ to the bottom node. You can do that to exactly one node. That's the one I pick. Then ...
jonk's user avatar
  • 78.3k
4 votes

Why does this op-amp circuit show current flowing like that?

why is it drawn like this Both the current direction arrow and the actual sign of the current need to be taken into account when establishing the true direction of current. Generally, the picture and ...
Andy aka's user avatar
  • 463k
3 votes

Where did this useful matrix decomposition come from for Nodal Analysis?

I'm no mathematician but I feel strongly this is related to the singular value decomposition (SVD) or eigendecomposition. I first came across SVD in the context of modelling MIMO communication ...
jramsay42's user avatar
  • 1,262

Only top scored, non community-wiki answers of a minimum length are eligible