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The measured power, current, and voltage delivered to a load are 100W, 1A, and 120V...

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t4trendesetter | Honors

Posted August 18, 2013 at 3:28 PM via web

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The measured power, current, and voltage delivered to a load are 100W, 1A, and 120V respectively.? How would I find the reactive current? http://static.panoramio.com/photos/medium/94840337.jpg

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valentin68 | College Teacher | (Level 3) Associate Educator

Posted September 9, 2013 at 5:21 PM (Answer #1)

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There are three different types power that can be measured in an alternative current circuit (see the attached figure).

First, it is the Real Power Pr which is the power that the resistive part of circuit consumes from the voltage source (or the real part of the power). It is measured in Watts and express the ratio (work/time) that a circuit can deliver on the exterior.

Second, it is the Reactive Power, Pr which is the power consumed by the reactive components of the circuit (L and C) ) (or the imaginary part of the power). It is measured in VAR (Volts*Amperes Reactive) and express how much power is lost from the driving source on the reactive components.

Third, it is the Apparent Power, Pa which is the total power that a circuit consumes from the driving voltage source (sum of the vectors P and Pr). It is measured in VA (Volts*Amperes).

Since in your data the power is measured in Watt, it means that it is a Real Power

`P =U*I_R`    means that `I_R = P/U =100/120 =0.833 A`

This is the resistance current (or the real current).

Also from the text data, the total current that the source supply (the apparent current or total complex current) is `I_T =1 A`

From these two values and the right triangle of currents we can compute now the reactive current.

`I_X = sqrt(I_T^2 -I_R^2) =sqrt(1 -0.833^2) =0.553 A`

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