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

AI Thread Summary
The discussion centers on calculating the current in the primary coil of a transformer, where the user initially calculates 5 Amperes based on a ratio method, but questions its accuracy. The current in the secondary coil is given as 2 Amperes, leading to the inquiry about the relationship between primary and secondary voltages and currents. The law of conservation of energy is referenced, stating that power is conserved, expressed as Vp * Ip = Vs * Is. Additionally, the formula P = V^2/R is mentioned as relevant for calculating power dissipation through load resistance. The conversation emphasizes the need for clarity on how the initial current value of 5 Amperes was derived.
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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