# LRC Circuit

1. Oct 13, 2009

### sully677

1. The problem statement, all variables and given/known data
An L-R-C series circuit is constructed using a 175{ \Omega} resistor, a 12.5uF capacitor, and an 8.00 mH} inductor, all connected across an ac source having a variable frequency and a voltage amplitude of 25.0V

At the angular frequency in part A, find the potential difference across the ac source, the resistor, the capacitor, and the inductor at the instant that the current is equal to one-half its greatest positive value.

2. Relevant equations

V=IZ

3. The attempt at a solution

I found the voltage for all of them and divided by 2 since the current is half, but I can't get the right answer.

2. Oct 13, 2009

### Andrew Mason

You are incorrectly assuming that the voltage and current are in phase. You have to determine the phase angle between voltage and current.

AM

3. Oct 13, 2009

### sully677

okay. so once the phase angle is solved for, where do you go?

4. Oct 14, 2009

### Andrew Mason

Use expressions for V and I as a function of time eg.:

$$I = I_0\sin{(\omega t)}$$

$$V = V_0\sin{(\omega t + \phi)}$$

What is the relationship between V0 and I0? What is the value for $\omega t$ when I = .5I0?

AM

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