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1. A resistor, capacitor and inductor are connected in series to an ac source wi

ID: 2098969 • Letter: 1

Question

1.     A resistor, capacitor and inductor are connected in series to an ac source with a frequency of 30 Hz and an rms potential of 40 V. The resistor has a value of 200 W, the inductor has a value of 4.0 H and the capacitor has a value of 6.5 mF.

a.     Calculate XL, XC, f, Z and Irms for this circuit. Does the circuit potential lead or lag the current?

b.     Sketch the phasor diagram for this circuit. Label all vectors and angles.

c.     What is the resonance frequency for this circuit?

d.     What is the rms potential across the capacitor?

Explanation / Answer

1.     A resistor, capacitor and inductor are connected in series to an ac source with a frequency of 30 Hz and an rms potential of 40 V. The resistor has a value of 200 W, the inductor has a value of 4.0 H and the capacitor has a value of 6.5 mF.

a.     Calculate XL, XC, f, Z and Irms for this circuit. Does the circuit potential lead or lag the current?

b.     Sketch the phasor diagram for this circuit. Label all vectors and angles.

c.     What is the resonance frequency for this circuit?

d.     What is the rms potential across the capacitor?


a, XL = 2 pi f L = 2*3.14* 30* 4 = 753.6 ohms

Xc = 1/2 pi f C = 1/2*3.14* 30* 6.5 *10^-3 = 0.816 ohms

in order it to be 816.2 it must be uF.

its a potential lag current.


Z^2 = 200^2 + (816.2-753.6)^2

Z = 209.56 ohms

Irms = Vrms/Z   = 40/209.56 = 0.19 A


c. resosnance frequency w^2 = 1/LC   = 1/ 4 * 6.5 uF

     w = 196 rad/s