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A load draws 10 A of current from a 120-V source. The voltage leads the currrent by...

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t4trendesetter | Honors

Posted August 16, 2013 at 10:56 AM via web

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A load draws 10 A of current from a 120-V source. The voltage leads the currrent by 36.9 degrees. How do I determine the resistive current?

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valentin68 | College Teacher | (Level 3) Associate Educator

Posted September 11, 2013 at 5:15 AM (Answer #1)

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The specified current in the problem text is the total current `I_T =10 A` shown in the figure. Because there are 3 components of the current (total, resistive and reactive), the voltage drop over all the components of the circuit is the same. It means the circuit is parallel.

Now, from the figure posted with the problem text, one can see that the resistive component of the current is just

`I_R = I*T*cos(theta) = 10*cos(36.9) = 8 A`

where `theta =36.9 degree` is the phase difference between the total and resistive currents.

From the currents right triangle one can now determine the reactive component of the current

`I_X = sqrt(I_T^2-I_R^2) = sqrt(10^2 -8^2) = 6 A`

The resistive current is I(R) = 8 A and the reactive current is I(X) =6 A.

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