- #1
znaya
- 18
- 0
Homework Statement
Consider, in the circuit from the image,
i1(t) = 5 cos(2t + 10º)
v1(t) = 10 cos(2t - 60º).
Find the value of the current ix(t).
Options given:
A: ix(t) = 9.9 cos(2t - 129.2º)
B: ix(t) = 9 cos(2t - 29.2º)
C: ix(t) = 99 cos(2t + 129.2º)
D: ix(t) = 0.99 cos(2t + 130º)
Homework Equations
Ohm's law.
V=IR
The Attempt at a Solution
My approach was, first calculate the amount of current produced by the voltage source, combining the R + C + L in series and ignoring the current source, the result was 2<-59º(or 1.03 -1.7j)
After I calculated the amount of current from the current source. I ignored the voltage source (short circuiting the circuit) and calculated L || (C + R) and the amount of current going to (C + R) is 11.86<-25.3º (or 10.7 -5.06j).
Finally i summed the currents:
1.03-1.7j + -(10.7-5.06j) ====> negative because it goes in the opposite direction from the one in the image.
The result was -9.67+3.36j or 99.7<-19.16º [+180º];
That is 99.7 < 160.84º or 99.7 cos(2t + 160.84º)
That is near option C but not exactly! What am I doing wrong?
Thanks for any help.