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simple transformer impedence circuit

maark6000

Feb 8, 2012
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so I'm going thru "Introduction to Electronics: DC/AC circuits" by Stephen Harsany, and it's great, but the typos are killing me! So I need help determining if the text leaves out a crucial piece of info.

Given a primary circuit with an AC voltage of 10v, a resistance of 200 Ohm, and a secondary circuit with simply "R load" attached, find the turns necessary in the transformer for maximum power transfer. The problem as I see it, is we don't know what the load is. I mean heck, we have a primary with an impedance of 200 Ohm, why not just have a 1:1 transformer and a load of 200 Ohms as well, there you go, maximum power transfer.

The answer in the back of the book btw is 3.16:1. Which to mean seems to indicate that they left off the fact that R load was supposed to be 20 Ohm. The 10 VAC doesn't factor as far as max power transfer, right? It's extra info we don't need.

Please correct me if I am wrong. Thanks in advance. Mark
 

Harald Kapp

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Nov 17, 2011
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I don't have access to the book, so I cant judge it. Some good information on power matching via a transformer is here.
I don't think you have to look this up. You grabbed the concept pretty well and your conclusion about Rload is correct. It is also correct hat the 10V is an unnecessary information because the impedance matching is independent of this voltage.
 

maark6000

Feb 8, 2012
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cool, thanks harald. like I said, the typos in this book are many, especially with regard to the answers in the back. I may post a few of the more egregious examples later so at least if someone googles it, there may be a resource to get the correct answer.

cheers!
 
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