- #1
diredragon
- 323
- 15
Homework Statement
For AC Circuit shown in the picture, ##C=60nF##, ##L=100uH##, ##X_3=-100Ω##, ##Z_2=50Ω## and ##Φ_2=\frac {\pi}{6}##. When the switch is closed the ammeter shows a current ##I_1=0.6A## and the voltmeter shows ##U_l=60V##. The measuring instruments mentioned are ideal. Calculate:
a) ##w##
b) effective value of ##E##
c) ammeter result ##I'_1## when the switch is open.
The Circuit:
Homework Equations
3. The Attempt at a Solution [/B]
The first thing i noticed is that the direction of current and voltage isn't given so I need to guess it. I started from the ammeter and guessed that the flow of current is downwards.
From there, ##U_1 = I_1*X1## = -60V## with a + sign at the top node. Once i have this voltage i can find the current ##I_2 = \frac {U_1}{Z_2} = -1.2A##. With the two currents meeting at the top node, the current ##I_l = I_c## of the top node equals ##I_l=0.6A##.
Since i have ##U_l = I_l*wL##, ##w = \frac{U_L}{I_lL} = 10^6## which is not the correct answer.
The answer should be ##w = \frac {\sqrt 3}{3}10^6##. I can't go on solving the other parts if the first is not correct. What did i do wrong?