Can transformers alter the resistance of wires in a circuit?

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Discussion Overview

The discussion centers around whether transformers can alter the resistance of wires in a circuit when activated. Participants explore the relationship between voltage, current, and resistance in the context of transformers, particularly focusing on the implications of power conservation and load reflection.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if transformers change the resistance of wires when turned on, linking it to the relationship defined by V=IR.
  • Another participant asserts that transformers do not change resistance and introduces the concept of reactance and reactive impedance as relevant factors.
  • A participant explains the operation of a perfect transformer, detailing how power is conserved and how the load affects the primary side based on the turns ratio, emphasizing that the transformer reflects the load to the primary side.
  • Another participant agrees with the explanation provided, noting that the load resistance is modified by the square of the turns ratio.

Areas of Agreement / Disagreement

Participants generally agree that transformers do not change the resistance of wires but rather reflect the load to the primary side based on the turns ratio. However, there is some contention regarding the implications of this reflection and the role of reactance.

Contextual Notes

The discussion does not resolve the nuances of how reactance interacts with resistance in transformer circuits, nor does it clarify the specific conditions under which the principles discussed apply.

ak33m98
Do transformers change the resistance of the wires inside then when turned on? The reason I ask is because I know that transformers can be used to change the ratios between voltage a current while keeping the power sent in and power sent out roughly equal, but since V=IR this must mean that the resistance in the output/secondary circuit changes as the ratio between V and I does
 
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No. Look into reactance and reactive impedance.
 
A transformer does not change the power IN/OUT much less do anything based on changing the resistance.

Let's talk perfect 2X step up transformer where there are 2 times the number of turns in the secondary as in the primary. You connect 50V AC to the primary and 50 ohms to the secondary. Since there will be 100V on the secondary (because of the 2:1 stepup) there will be 2A in the load. 2A at 100V = 200W. That means there must be 200W flowing into the primary (where else can the power come from?), or 4A. If you change the resistance to 100 ohms, there will be 1A, 100W so there will only be 100W into the primary of the transformer, or 2A.

So, what ever the power consumed by the secondary load, the power flowing into the primary will be just enough to supply that power. The perfect transformer has no power loss. You could say that the transformer "reflects" it load to the primary based on the turns ratio.

With that in mind, read the wikipedia article.
http://en.wikipedia.org/wiki/Transformer
 
upload_2015-1-1_21-52-11.png

I agree, of course, with meBigGuy.If you look from primary you see Rload modified by ratio (w1/w2)^2
where :
w1=primary winding number of turns
w2=secondary winding number of turns
 

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