Short circuit confusion, when is the resistance 0

[Frankenstein19]

Homework Statement

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I'm going exercises and I understand that if the circuit is short circuited that R=10 ohm is 0. (Trying to find Thevelin R in all of these btw)

But then I ran across this one where when it's short circuited, isc is found using the current divider principle and it's R1/(R1+r2), why doesn't R1 turn to zero?

 

[phinds]

But then I ran across this one where when it's short circuited, isc is found using the current divider principle and it's R1/(R1+r2), why doesn't R1 turn to zero?

Is R1 in parallel with the short?

 

[Frankenstein19]

Is R1 in parallel with the short?

Yes...? If there's a resistor in between does that make them stop being in parallel?

 

[phinds]

Yes...? If there's a resistor in between does that make them stop being in parallel?

I suggest that you go back and study over and over the fundamentals of series and parallel. You HAVE to get that totally straight before trying ANY circuit problems and you have some confusion.

 

[gneill]

Yes...? If there's a resistor in between does that make them stop being in parallel?

Yes. If you can't follow a closed path passing through the two components that does not have to pass through any other component along the way, then they are not parallel-connected. Put another way, if two components are parallel-connected, then you can draw a closed path that passes only through that pair of components.