Source transformation, current & voltage sources

[ace8888]

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color]

Hi,

I was working on a the source transformation and i got to the part where there are two current sources in the circuit. The current sources were added together (giving they were going in the same direction). This is the part that confused me.

1. Was KCL done at the common node on the top to get the sum of the two current sources?? if so we didnt account for the current of R1 & R2? How can we just add two sources ( i know they are going in the same direction) and ignore the rest of the components?

2. On one of the posts that i read stated, In series the voltage would add and in parallel the current will add?

Please provide explanation/derivation as I'm confused.

thank you!

 

[scottdave]

There are no components between the tops of the current sources (or the bottom either). The total current entering the node is equal to the total current exiting the node. So yes, in this case you can combine them to a single 6 mA source.

 

[ace8888]

There are no components between the tops of the current sources (or the bottom either). The total current entering the node is equal to the total current exiting the node. So yes, in this case you can combine them to a single 6 mA source.

That same node also has current from the both resistors so when you're combining it into one where are those two currents? That was my question if KVL was done at the top node, you don't account for the current of R1 and R2??

 

[scottdave]

Some of that 6mA will exit through R1, and some will exit through R2. What you want to do, is find an equivalent resistance of R1||R2, then find voltage of 6 mA through this resistor.