What voltage appears across the primary coil of this transormer

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    Coil Voltage
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Homework Help Overview

The problem involves a step-down transformer and seeks to determine the voltage across the primary coil when a specific voltage is applied to the secondary coil. The context includes understanding transformer relationships and voltage ratios.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the voltage ratio between the primary and secondary coils, questioning how to apply the given voltage to the secondary coil in the context of the transformer equations. There is confusion regarding the interpretation of the voltage applied to the secondary coil and its mathematical implications.

Discussion Status

Some participants have offered guidance on the correct application of the voltage ratio, while others are exploring the implications of applying 120 V to the secondary coil. There is a recognition of mistakes made in calculations, but no consensus on the final answer has been reached.

Contextual Notes

Participants are navigating through the relationships defined by transformer equations and are addressing potential misunderstandings about how to manipulate these ratios with the given voltages.

carrieunder
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Homework Statement


A step down transformer produces a voltage of 6.0 V across the secondary coil when the voltage across the primary coil is 120 V. What voltage appears across the primary coil of this transormer if 120 V is applied to the secondary coil?


Homework Equations



Vp/Vs=Np/Ns=Is/Ip .... ? (not sure if that is relevant really)

The Attempt at a Solution



i know Vs/Vp = 120/6

i think i don't really know what to do with the 120 v applied to the secondary coil
i added 120 to the 6 = 126 that means 6 was multiplied by a factor of 21
so i multiplied the top value of the ratio (120) by 21 and got 2520 v
but I am really not sure if that's right at all? what does "120 V is applied" in mathematical terms?
 
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You've got everything so right, I'm not sure how you can go wrong. Vs/Vp=120/6=20. So if Vp=6V, Vs=20*Vp=120V. Now suppose Vs=120V? Where is the 21 factor coming from? You don't add the secondary to the primary, it's just a ratio.
 
Last edited:
ok i get it i made a stupid mistake
so its really 120 X 20 right?
so the answer is 2400 ?
 
carrieunder said:
ok i get it i made a stupid mistake
so its really 120 X 20 right?
so the answer is 2400 ?

Yes.
 

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