Source Transformations, Confusion

Discussion in 'Homework Help' started by jegues, Oct 1, 2010.

1. jegues Thread Starter Well-Known Member

Sep 13, 2010
732
45
See figure attached for problem statement.

I'm supposed to find the power supplied by each one of the sources so I started by transforming other branches aside from the one that contains the 8V source.

I've transformed the original circuit to this point and now I'm stuck.

I don't know what move I can make next without making a mistake.

Can I combine the two voltage sources that are in parallel?

Can I combine any of the 3 resistors in parallel?

I could think of a few things to do but I'm not confident enough to actually make those moves in fear that I'm doing something wrong.

Can someone clarify or help me identify what I'm looking at here?

Thanks again!

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2. Fraser_Integration Member

Nov 28, 2009
142
6
I think you probably have done enough transforming to work out the power delivered by each source.

You can now label up your nodes and perform a node-voltage-method or mesh-current-analysis solution depending on what you prefer. there are notes on both of these useful things on the online textbbook.

remember that the power delivered by a source is the current through it times the voltage across it. watch out for polarities.

3. Fraser_Integration Member

Nov 28, 2009
142
6
looking again, mesh current method would be the easiest way to do it. good luck

4. Ghar Active Member

Mar 8, 2010
655
73
I think node voltage is easier because there's only 3 nodes with 2 nodes constrained by the 8V source.

With mesh current there's 3 meshes with no knowns.

5. Fraser_Integration Member

Nov 28, 2009
142
6
oh yeah, quite right I didnt notice the useful little 8V supply when earlier.

I just did it the mesh current way (Uni starts again next week, need the practice!) and it took a whole page of scribbling.

6. jegues Thread Starter Well-Known Member

Sep 13, 2010
732
45
The whole point of the exercise is to solve using solely source transformations. I'd like to know how I can continue to use them until I can solve the power out of the 8v source.

I could transform the two voltage sources on the outsides into current sources with parallel resistors then combine all 3 parallel branches together, no?

7. Ghar Active Member

Mar 8, 2010
655
73
I don't think so, the 8 ohm will never be in series or parallel with the 25 ohm because of the connection to the 8V source.

If you did a y-to-delta transform on the 25-20-10 ohm resistors you could continue with source transforms...