I've built the scheme below in circuit simulator and it didn't work because of "wire loop" mistake. Why it's wrong? Why it's wrong physically?

The simulator is falstad.com/circuit

enter image description here

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    \$\begingroup\$ Why something is wrong "physically" has little relationship to why a circuit won't work in a simulator. \$\endgroup\$
    – Andy aka
    Dec 9 '18 at 16:56
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    \$\begingroup\$ Which simulator? It might just be upset that it can't determine how much current flows through each wire. \$\endgroup\$
    – The Photon
    Dec 9 '18 at 16:57
  • \$\begingroup\$ @Andyaka why it doesn't work in a simulator? \$\endgroup\$ Dec 9 '18 at 16:58
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    \$\begingroup\$ Yeah, Falstad will want to know the current in each wire so it can do its cutesy animations. In this circuit, that can't be determined so Falstad will consider it an error. \$\endgroup\$
    – The Photon
    Dec 9 '18 at 17:01
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    \$\begingroup\$ Circuit simulators deal with idealized wires, which have zero resistance (and zero inductance, and zero capacitance). To model a real-world circuit that looks like what you drew on paper, estimate the resistance of each wire and put resistors into each leg in the circuit simulator. \$\endgroup\$
    – TimWescott
    Dec 9 '18 at 17:17

Two parallel wires with no resistance - why it's wrong?

This is wrong because there are no wires with no resistance. When trying to resolve Kirchhoff equations for this loop (or whatever their algorithm is), the simulator would run into division by zero exception. To avoid program crash, it likely analyzes these conditions and declares the circuit as error. Try to replace wires with resistors with micro-Ohms value (or maybe even less), it should be fine.


Falstad wants to be able to animate the circuit, showing how much current flows in each wire.

In this circuit, that isn't possible, so it is indicating this as an error.

  • \$\begingroup\$ I meant 100 Omhs, and it's not about wires, it's about resistor, that is near upper potential point. In real life, how much current will flow through one of parallel wire? \$\endgroup\$ Dec 9 '18 at 17:11
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    \$\begingroup\$ The total current between the two wires will be whatever the supply voltage is divided by 100 ohms. But you can't tell how much will flow through one wire and how much through the other. That's the whole problem. \$\endgroup\$
    – The Photon
    Dec 9 '18 at 17:15
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    \$\begingroup\$ @АртурКлочко, in real life the current will be split in inverse proportion to real-life impedance of each wire, be this in micro-Ohms or else. \$\endgroup\$ Dec 9 '18 at 17:46

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