Thevenin Theorem

[Student323]

Hi All,

I am studying for my FE Exam and I stumbled upon a concept that is very confusing.

Sometime some example tell me to ignore the resistors facing the short circuited voltage source, other times it seems like i do not need to.

For example, this problem here does not ignore the 6ohm resistor after the voltage source is shorted

savvy-engineer-nuxt

My funkadelic Nuxt.js project

savvy.engineer

whereas for this example, the 6ohm is ignored. The only conclusion i can think of is when the resistor is in parallel with a shorted voltage source, it can be ignored.

Thévenin equivalent voltage: why ignore the 16 Ω resistor?

I am really confused by the concept of ignoring resistors while doing Thévenin theorem, especially for this problem. Some online videos, like this one, and other examples that I watched seem to sug...

electronics.stackexchange.com

Any insight will be greatly appreciated

 

[LarryFine]

The only conclusion i can think of is when the resistor is in parallel with a shorted voltage source, it can be ignored.

Agreed. The 6 ohm resistor is in series with the short, while the 16-ohm resistor is in parallel with it.

 

[charlie b]

The equivalent of two parallel resistors is their product divided by their sum. A short circuit in parallel with a 6 ohm resistor is equivalent to (0 × 16) / (0 + 16), or zero ohms. That is why you can ignore the 6 ohm resistor in the second question.

 

[Student323]

Thanks for confirming everyone, that makes more sense