Failing in Analyzing these (unusual) circuits

In summary, Kirchhoff's laws would not apply to a circuit with a magnetic field because the flux is changing. This can be seen in the diagram where the black line between the two wires is the limitation/airgap. The voltage at point (a) would be the sum of VPS and Vwire.
  • #1
PhiowPhi
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I'm studying more (odd) circuits, where Kirchhoff law's would fail because of a magnetic field being part of a circuit, and it's flux is changing.
For example this circuit:

0QMp1K5.png


PS(##V_P##)is an external power source connected to the circuit, where there is a wire that an external magnetic field is changing, the change in(##B##) is negative, therefore inducing an EMF(##V_E##) is positive:

##V_E## = -##\frac{ \Delta (-B)A}{ \Delta t}##

The wires(two of them) the right hand one being inside a magnetic field, the other isn't are split in a way to reduce Eddy currents the black line in between is limitation/airgap.

I know that the direction of current is correct, as diagrammed. However, at point (a) what would be the total voltage there? What voltage would the load(R) see(or receive for a better word,even though it's voltage we're talking about, ...)? Is it simply ##V_P## + ##V_E##?
It's odd to figure out without KVL.

It might be much easier to apply the magnetic field on both parallel wires like so:

m9rytOB.png

Now, we could assume the induced EMF to larger due to the area increase at the same given time, at the same change of magnetic field, here it's intuitive for me to assume the voltage would be ##V_P## + ##V_E##.

Also, like to add for the first diagram it's only two wires but what if there are a lot more wires on the left side(not inside the magnetic field)?
 
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  • #2
I = VPS÷R

The magnetic circuit is shorted out and thus contributes nothing.

Or the magnetic circuit provides whatever you want, since it is not well defined. We really can't eliminate the eddy current, then drop a voltage across a 0Ω wire.

In a real circuit, there would be an eddy current traveling through the (non-magnetic) wire which would cause a small voltage equal to the eddy current times the wire's resistance. (I'll call that Vwire.) That would add to VPS. (Va=VPS+Vwire)
 
  • #3
I guess the second intuitive question would be: Why would the magnetic sub-circuit short? Given a load with finite resistance.
Why wound't the voltages add up? If there is already a small voltage due to Eddy currents( equal to I(Eddy's)xR) that add up the VPS.
 
  • #4
It's nice to see you thinking. Having a deeper understanding than just grinding numbers will serve you well.

The magnetic sub-circuit can be modeled as the secondary half of a one turn transformer with a wire shorting the terminals. Since, for circuit analysis, wires are considered shorts with 0Ω, it shorts with an infinite current. (You can stretch the model by adding wire resistances and eddy currents to get an answer.)

In your second drawing, the wires could be modeled as two secondary transformers. Those would not be shorted.

It's important to understand that circuit analysis is a model, not reality. There are conditions where it breaks down. For example it is not great for distributed transmission lines. (It can be made to work by lumping elements, but there are better models.)
 
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1. How do I determine if a circuit analysis has failed?

A circuit analysis can be considered failed if the results do not match the expected values or if the analysis process does not follow logical and consistent steps.

2. What are some common reasons for failing in analyzing unusual circuits?

Some common reasons for failing in analyzing unusual circuits include incorrect assumptions, faulty equipment, and unexpected circuit behavior due to faulty components or improper circuit design.

3. What steps can I take to avoid failing in analyzing unusual circuits?

To avoid failing in analyzing unusual circuits, it is important to thoroughly understand the circuit components and their behavior, double-check all assumptions and calculations, and use reliable equipment for testing.

4. How can I troubleshoot a failed circuit analysis?

To troubleshoot a failed circuit analysis, it is helpful to review all assumptions, calculations, and steps taken during the analysis process. Additionally, testing individual components and using simulation software can help identify the source of the failure.

5. Are there any tips for successfully analyzing unusual circuits?

Some tips for successfully analyzing unusual circuits include breaking down the circuit into smaller, simpler sections, using a systematic approach, and consulting with other experts or references for guidance. It is also important to have a thorough understanding of circuit theory and techniques for solving complex circuits.

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