What is the Power Loss in a Transformer?

[DaveE]

OK, only slightly off-topic...

I am so G%$D%$@ tired of students being confused and asking questions that are solely the result of the apparent fact that their instructor is an idiot or too lazy to write comprehensible questions. This seems to be about 80% of the EE questions I see here. I think it's really unfair to confuse people that are new to a subject. They just don't have the background to question the quality of their course work; they think they don't understand, when, in fact, it's not understandable.

Sorry, I'm frustrated and needed to vent. Y'all can go back to this seemingly unending discussion about missing information.

 

[annamal]

Ok but your solution attempt indicates that you are looking for the power loss in the secondary of the transformer.

That's what the answer key says the solution is, which I am trying to ask how they figured it out.

 

[haruspex]

That's what the answer key says the solution is, which I am trying to ask how they figured it out.

I think we have consensus that the given solution is nonsense.

My best guess is that the problem statement was supposed to tell you that the resistance of the transmission line is 200 Ohms (as assumed in the solution to part d), and that that value should have been used in part c, not 6000 Ohms. 200 still seems a bit high to me, but 6000 for a transmission line is ridiculous.

This is the message I sent to OpenStax:
Message: I wish to draw your attention to some misinformation on your website at https://openstax.org/books/university-physics-volume-2/pages/15-6-transformers. Part c of the example 15.6, Step-Down Transformer, is nonsense.
The question is unanswerable with the given data because there is no way to determine the resistance of the transmission line. The 6000Ohms used in the solution appears to be the combined resistance of the transformer and the downstream load. (I believe typical transmission lines have resistances of a few tens of Ohms at most.)

 

[alan123hk]

My best guess is that the problem statement was supposed to tell you that the resistance of the transmission line is 200 Ohms (as assumed in the solution to part d), and that that value should have been used in part c, not 6000 Ohms. 200 still seems a bit high to me, but 6000 for a transmission line is ridiculous.

The ohmic resistance of a transmission line is really hard to estimate and depends on many factors.
In this example, the input power of the transformer is $12KV\cdot 2A=24KW$. If the ohmic resistance of the transmission line is 6000 ohms, then its $~2^2\cdot6000=24kW~$power loss is as high as the input power of the transformer. I don't think the power company will accept it.
Also, this question is really confusing. If you get a reply from OpenStax, please share the answer to this unsolved mystery.

 

[Herman Trivilino]

OpenStax is riddled with errors like this.

 

[vela]

OpenStax is riddled with errors like this.

What's funny is that this example is mentioned in the errata for the book and supposedly was reviewed/corrected just last year. Leaving out part (d) in the problem statement itself seems like a pretty big error to miss.