# handling of sources in a circuit

Discussion in 'Homework Help' started by jalisco, Jul 3, 2012.

1. ### jalisco Thread Starter New Member

Jul 3, 2012
1
0
Hi, the following circuit was a question I just had on a test.

The question was to simplify/re-draw it, and find various values throughout the circuit.

the problem I had was handling the sources. I really was stuck there.

I know the basics of a current to voltage conversion using the inner resistance and if there is a corresponding - serial or parallel resistor, respectively.

But, this case, the circuit is beyond what I have done in example problems. Any help to understanding how to handle and simply the sources would be deeply appreciated. =)

Thanks! No rush, unfortunately, I already took the test and didn't gets points for this problem =( But, I still want (and need to know) for the future =)

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2. ### WBahn Moderator

Mar 31, 2012
23,093
6,946
What you can do to simplify it depends on what it is you are looking for. You can't incorporate into a source conversion any component that you want to know the voltage or current for.

As shown, it appears you are trying to find the currents in both E1 and E2. You can either simplify the circuit while keeping both sources intact, or you can simplify until you only have one of them, solve for that current, and then redo things (at least partially) to solve for the other.

Another alternative that should work well in this problem is superposition.

Assuming that you aren't being asked for information about the current source or any of the resistors:

Q1) What is the parallel combination of R1 and R2 (call it R12)?
Q2) What is the Thevenin voltage source that is equivalent to I1 and R12?
Q3) Can resistors R3 and R4 now be combined with the Thevenin source resistance?
Q4) Can this Thevenin source now be converted to a Norton source?

At this point, you could focus on the current in E2.

Q5) Can the E1 source and its series resistor be converted to a Norton source?
Q6) Can the two Norton sources be combined into a single Norton source?
Q7) Can this combined Norton source be converted to a Thevenin source?
Q8) Can the current in E2 now be solved for simply?

3. ### dataman19 Member

Dec 26, 2009
136
30
So the instructor wanted you to draw a dual parallel resistor circuit using R1 & R2.. - Calculate the values....
Then he wanted you to draw a series circuit with R3 in series with (R5 & R6 - in parallel) and R4 in series (so the series circuit would be
R1+
(R5 & R6 - use this formula , sub R5 & R6 for R1 & R2)
( )