Problem in identifying a short circuit in a diagram

[Amaelle]

Hi all!
while simplifying this diagram, I thought that R2 and R4 are in parallel
while

so I simplified the diagram to this

BUT THE SOLUTION CONSIDER THAT R4 AND R2 HAVE BEEN COUR CIRCUITED!
Any help would be highly appreciated particularly a rule of thumb that helps me to identify a short circuit with a fault!
many thanks in advance!

 

[NascentOxygen]

In your top schematic, R5 R4 R2 R3 all share a common node. In your "simplified" schematic, this feature has been lost, so it is not equivalent.

 

[Amaelle]

thank you! BUT HOW COULD THEY SAY THAT R4 AND R2 ARE SHORT CIRCUITED?

 

[Merlin3189]

DID they say, "R4 and R2 are court circuit" ? Else what did they actually say or show in a diagram?

They are in parallel. They are significant and not short circuited. But your diagram is in no way equivalent to the original circuit. You have removed the connection between R3 and R5. In your diagram you have connected R3 to the opposite end of R2 and R4 from the original diagram.

I would suggest you label the nodes and note which nodes the components connect to.

 

[Amaelle]

thanks a lot for your prompt reply,
let start from the begining:
the exercice ask to calculate the current i(t)

so i simplified the circuit as follow considering that R4 and R2 are parallel ( the circuit is not equivalent to the first but i guess the value i(t) will not change (please correct me if I'm wrong)

then I simplified further the circuit by using the conversion between the current generator a1(t) and it's voltage generator equivalent

after this step I used millman theorem to compute the potential between the nodes 4 and 3

and then divide by the resistance of the branch to find i(t)

the problem is that in solution they totally ignore R4 and R2 as they short circuited!

many thanks in advance!

 

[gneill]

If you begin with:

and combine R₂ with R₄ you get this:

 

[Amaelle]

you are awsome! thanks a million you totally solved my problem! God bless you!

 

[eq1]

If you begin with:

gneill,
I know it's off-topic, but what did you use to create those circuit diagrams? They look nice, and it seems like you were able to draw them quickly.

 

[gneill]

gneill,
I know it's off-topic, but what did you use to create those circuit diagrams? They look nice, and it seems like you were able to draw them quickly.

I use an ancient copy of Visio. I created my own template for electronic symbols (the one that came with Visio was incomplete a rather crude).

 

[DaveE]

Also a bit off topic:
For more readable schematics avoid any connections that have 4 "wires" leaving from a single node. Try to make all connections "T intersections" with large dots. This avoids the confusion of whether connections are joined or crossing. Then all 4 wire nodes are crossing, by definition.
Back in the day this was an absolute Mil-Spec requirement for schematics because poor quality reproductions could add or remove the dots that indicate connections.