Question 17, chap 133, sect 7. part 1 of 4 10 points A coil is connected to a 70

Question

Question 17, chap 133, sect 7. part 1 of 4 10 points A coil is connected to a 70 Hz, 110 V AC generator. At this frequency, the coil has an impedance of 10 ohm and a reactance of 4ohm. What is the current in the coil? Answer in units of A. Question 18, chap 133, sect 7. part 2 of 4 10 points What is the phase angle between the current and the applied voltage? Answer in units Question 19, chap 133, sect 7. part 3 of 4 10 points What series capacitance is required so that the current and voltage are in phase? Answer in units of MuF.

Explanation / Answer

impedence Z^2 = R^2 +(Xl-Xc)^2 = 10 ohms

so Current i = V/Z = 110/10 = 11 Amps
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18.

phase angle tan theta    = XL-XC/R =

use Z^2 = R^2+XL^2

so R^2 = 10^2-4^2

R = 9.16 ohms

so tan theta = 4/(9.16)

theta = phase = 23.57 deg
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to be in resosnance W^2 = 1/LC

C = 1/W^2L

XL = 2pifL = 4

L = 9 mH

C = 1/(2*3.14*70)^2 * 9 e-3

C = 575 uF

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