Is current measured in Watts or kW?

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Homework Help Overview

The discussion revolves around the measurement of current and power in electrical systems, specifically in the context of transformers. The original poster seeks clarification on whether current is measured in Watts or kilowatts while working with the equation relating primary and secondary voltages and currents.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between power and current, questioning the correct units for measurement. There is an attempt to apply the power equation in the context of a transformer, with some participants checking assumptions about efficiency and unit conversions.

Discussion Status

Participants have provided guidance on the correct application of the power equation and the need to differentiate between power and current. There is an ongoing exploration of the calculations involved, with multiple interpretations of the problem being discussed.

Contextual Notes

Assumptions about the efficiency of the transformer are noted, and there is a focus on ensuring the correct use of units in calculations. The original poster's confusion regarding the measurement units is a central theme in the discussion.

JosephF
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Homework Statement



I'm using the following equation:

Is Vs = Ip Vp

Is the current measured in Watts or kW?

Homework Equations



n/a

The Attempt at a Solution



n/a
 
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well power is measured in Watts, not current.
 


Ok. I'll show you the question and hopefully I've gone in the right direction.

Homework Statement



A power line supplies electrical energy to a transformer in a manufacturing plant.
The input voltage to the transformer is 11,000V. The transformer changes this to 415V for use in the manufacturing plant. The power input to the transformer is 800kW.

i. Calculate the current in the secondary coil of the transformer, stating any assumptions you have made about the transformer.

Homework Equations



[tex] <br /> I_p V_p = I_s V_s<br /> [/tex]

The Attempt at a Solution



Assuming 100% efficency in the transformer.

x / 415 = 800,000 / 11,000

x = 30.181 (3dp) kW

I think I'm using the right equation but have I got my units mixed up?

Thanks,
 


you are using the right equation except that you have substituted the power as the current!
you need to get the primary current using P=IV
then you can use that equation =]
 


i get 1927.7 Amps, is this correct?
 


I also got 1927.7108...

Thanks for your help Rory :)
 


Excellent!
No worries JospephF =]
 

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