# Can someone clarify the connections between these concepts?

1. Feb 22, 2013

### InvalidID

I've learned some concepts in my Electric Circuit Analysis course:

• Ohm's law
• KCL + KVL
• Voltage Division (derived from Ohm's law + KVL)
• Current Division (derived from Ohm's law + KCL)
• Y-Delta transformations
• Nodal Analysis (derived from Ohm's law + KCL)
• Mesh Analysis (derived from Ohm's law + KVL)

So it seems that you can solve any circuit problem using nodal analysis and mesh analysis alone, right? Is there any benefit of the old method of solving circuits (using KCL & KVL)?

Is there any benefit of using voltage division and current division when applying nodal and mesh analysis? I remember that when solving circuits through the use of KCL & KVL, you would sometimes need to apply voltage and current division. But because both divisions and both nodal & mesh analysis are derived from a combination of Ohm's law and Kirchhoff's laws, then the divisions are no longer necessary when solving a circuit using nodal/mesh analysis, right?

2. Feb 22, 2013

### jsgruszynski

Node and Mesh analysis use KCL and KVL. They are NOT separate concepts.

IIF the circuit is linear, you can solve with just these. Nonlinear circuits require numerical methods or approximations to be made (e.g. hybrid pi linearization).

3. Feb 22, 2013

### tomizzo

What the above user said. Also, with current and voltage division, there are times where that will be the most logical and simple way to calculate some values. There is no reason to use KCL(Nodal Analysis) and KVL(Mesh/Loop Analysis) when you're trying to find an answer quickly.

4. Feb 22, 2013

### InvalidID

So I understood you two correctly, the answer to my questions would be as follow?

So it seems that you can solve any circuit problem using nodal analysis and mesh analysis alone, right? Only linear circuits.

Is there any benefit of the old method of solving circuits (using KCL & KVL)? No there is no benefit of using KCL/KCL over mesh/nodal analysis, because they're the same concept.

Is there any benefit of using voltage division and current division when applying nodal and mesh analysis? No. Voltage/current division is only handy when you want to do a quick calculation. You can still use nodal/mesh (or KVL/KCL) to get the same exact answer.

I remember that when solving circuits through the use of KCL & KVL, you would sometimes need to apply voltage and current division. But because both divisions and both nodal & mesh analysis are derived from a combination of Ohm's law and Kirchhoff's laws, then the divisions are no longer necessary when solving a circuit using nodal/mesh analysis, right? Yes.

5. Feb 26, 2013

### carlgrace

Knowing both KCL/KVL and mesh are useful... they are the same concept but sometimes one is easier than the other.

Also, these techniques are often used in active circuits where we use linear models for the active devices. They are worth knowing!

6. Mar 2, 2013

### Ratch

Invalid,

Don't forget the branch analysis method: http://www.daenotes.com/electronics/basic-electronics/branch-current-method#axzz2MRkoAOPU . Also simplification using supernodes and superloops Then there is Thevinin's and Norton's theorms. In addition you have to deal with independent and dependent voltage and current sources.

Certainly, it gives you an answer.

And what concept is that? If you have a circuit with 5 nodes and 3 loops, using the loop method would mean you solve for three unknowns instead of 5 unknowns.

Yes, it can simplify the circuit.

Nodal and loop analysis always work, but voltage proportion and current division can help simplify a circuit.

Ratch