Calculating Current in Primary Coil: Where Does P = V^2/R Formula Come In?

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Homework Help Overview

The discussion revolves around calculating the current in the primary coil of a transformer, specifically exploring the relationship between primary and secondary currents and voltages. Participants are examining the application of relevant electrical formulas and principles, including the conservation of energy.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants attempt to calculate the primary coil current using a ratio proportion method based on the secondary coil current. Questions arise regarding the correctness of this approach and the relationship between voltages and currents in the coils.

Discussion Status

There is ongoing exploration of the calculations and relationships involved, with some participants questioning the assumptions made about the number of turns in the coils and the validity of the derived current. Guidance is offered regarding the conservation of energy, but no consensus has been reached on the correct current value.

Contextual Notes

Participants note the absence of information regarding the number of turns in the primary and secondary coils, which is crucial for accurate calculations. Additionally, there is discussion about the application of the formula P = V^2/R in the context of power dissipation through load resistance.

Muhammad Danish
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Homework Statement


upload_2018-4-16_21-12-28.png

Homework Equations


How will we calculate the current in primary coil?

The Attempt at a Solution


The current in the secondary coil will be 2 Amperes by I = V/R. So in the primary coil by using ratio proportion method, the current in the primary coil will be 5 Amperes. But this leads to wrong answer.
 

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Show work for how you come up with 5A for the primary coil current as a starting point...
 
Muhammad Danish said:
The current in the secondary coil will be 2 Amperes by I = V/R. So in the primary coil by using ratio proportion method, the current in the primary coil will be 5 Amperes. But this leads to wrong answer.

is there a relation between Vp Vs and Ip , Is ? ultimately they are related to number of turns also.
 
SunThief said:
Show work for how you come up with 5A for the primary coil current as a starting point...
600V ---- x
240V ---- 2
Since they are directly proportional, we can get x = 5 ampere but I don't think this is a correct answer..
 
drvrm said:
is there a relation between Vp Vs and Ip , Is ? ultimately they are related to number of turns also.
But number of turns in primary and secondary coil are not mentioned..
 
By law of conservation of energy - power is conserved in the input and output

Vp . Ip = Vs. Is

.
 
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drvrm said:
By law of conservation of energy - power is conserved in the input and output

Vp . Ip = Vs. Is

.
Oh Thanks, by finding Ip I can find the power dissipated by the formula P = IV right?
 
Muhammad Danish said:
Oh Thanks, by finding Ip I can find the power dissipated by the formula P = IV right?
Just to increase knowledge, where do we use the formula P = V^2/R ?
 
Muhammad Danish said:
Just to increase knowledge, where do we use the formula P = V^2
R
its v^2/R
both forms are equivalent...if one is calculating dissipation through load resistance R its good
but how you got 5 amp as current?.
 

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