- #1
craka
- 20
- 0
Homework Statement
AC circuit Vs is 100V 50Hz and is used as reference.
there are two impedences in parallel, made up of a 5ohm resistor and an inductor reactance = +j2 ohm that is parallel with 3 ohm resistor and a inductor reactance = -j3 ohm (though I though negative imaginary part was for capactance?)
voltage across the 3 ohm resistor is 45 Volts
The branch with the resistor and inductor is called I1 , branch with resistor and capacitor is I2
Is is the total current from supply before the parallel branch.
Please see attachment of circuit
Homework Equations
I2 = v/I angle = arctan x/r
Is = Vs/Zt = Vs * 1/ (Z1 parallel Z2) = Z1Z2/(Z1+Z2)
The Attempt at a Solution
I2 = 45/3 =15A angle = artan -3/3 = -45 degrees
magnitude of Vs = 15 * sqrt(3^2+3^2) = 63.64 volts
Z1 = 5+2j = 5.385 angle 21.8 deg Z2 = 3-3j = 4.234 angle -45 deg
Z1//Z2 = {(5.385 angle 21.8) * ( 4.234 angle -45)}/ {(5+2j)+(3-3j)}
Z1//Z2 = 22.849 angle -23.2 deg / 8.06 angle -7.125
Z1//Z2 = 2.835 angle -16.075 deg
Is = 63.64/(2.835 angle -16.075) = 22.45 angle -16.08 degFrom here is where I'm lost on how to calculate the frequency needed to get this circuit to have current and voltage in phase (zero degrees)