# Homework Help: Finding the frequency of a series parallel circuit using complex notation

1. May 30, 2012

### Karma1

The frequency, ω, of the source in the circuit of Figure 2 is adjusted until ig is in phase with vg.

(a)using complex notation, determine the value of ω (rad/sec)

Can anyone out there please help with this question? Ive tried multiple methods but Im really struggling with simplifying the equation and my answers are wildly inaccurate.

(Please see attached document for details of the circuit)

#### Attached Files:

• ###### Complex Circuit.png
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2. May 30, 2012

### Staff: Mentor

You'll have to demonstrate an attempt so that we can see how to help.

3. May 31, 2012

### Staff: Mentor

Hi Karma1! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

To get you started, at a frequency ω, what is the impedance of 1kΩ || 500mH? Express your answer in the form: a + jb

Last edited by a moderator: May 6, 2017
4. May 31, 2012

### Karma1

Hey NascentOxygen,

I havn't got a clue where to start I'm sorry.

5. May 31, 2012

### Karma1

This is what I've managed so far.

#### Attached Files:

• ###### Complex Calculations.jpg
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6. May 31, 2012

### Staff: Mentor

j is not zero; j is the square root of -1. What is zero at resonance is the imaginary term of the impedance.

You've got the correct approach for determining the impedance. What you need to do is separate it into its real and imaginary parts; write it in the form: [real part] + j[imaginary part], and then deal with finding a value for ω that makes [imaginary part] zero.