# An equivalent resistance with a short

simulate this circuit – Schematic created using CircuitLab

This schematic is giving me trouble because of the connecting wire shown in red. What is the equivalent resistance of the circuit, as seen from the blue terminals?

• Comments are not for extended discussion; this conversation has been moved to chat. Jun 9, 2020 at 18:45

## 2 Answers

As it is clear that R1 is short circuited by that red wire,the equivalent resistance will be the parallel combination of R2,R3,R4.....

• I added a current source just to clarify my following question, which I hope is alright. If R1 is shorted, as Brian also mentioned, does that not mean that all current goes through R1, therefore the effective equivalent resistance of this circuit (as I now understand this is how one is supposed to understand circuits like these) is R1? May 28, 2020 at 17:24
• Your answer has been put of of date by an amendment to the question but, nevertheless you shouldn't be so hasty to answer with questions like this because giving the answer on a silver plate doesn't really help. May 28, 2020 at 17:35
• I disagree Andy, this outcome is far more interesting and helpful, and would not have been brought about without this answer. May 28, 2020 at 17:50
• The original circuit has been returned, thus user244617's answer remains applicable. May 28, 2020 at 19:03

Note: OP (on my recommendation) brought this question here from physics.SE after it was closed for being homework-like: (Original question with hand drawn schematics here)

In that original question, OP is attempting to use superposition to solve the circuit with both a current and voltage source. Voltage source (in series with R4) has been zeroed leaving only the current source. OP wants to find voltage across R3 (voltage reference direction is top-most terminal positive).

To this end, OP asks (there) for the equivalent resistance for a current division (CD) calculation.

But, on my view, OP isn't clear on current division. I explained (there) that it must be done twice, i.e., find the current through R4 using CD and, having that, further find the current through R3 using CD. The voltage across follows from Ohm's law.

It's been some time since I've answered here, and I don't want to run afoul of the homework policy here. So I won't give the simple calculation but I will give this hint:

The only equivalent resistance required is that of the branch in parallel with R1 for the first CD calculation.