# Homework Help: AC Voltage output across Resistor

1. Jun 10, 2010

### tomeatworld

1. The problem statement, all variables and given/known data
For the circuit below (attached) plot the amplitude of AC voltage across resistor as a function of the angular frequency of the ac source.

2. Relevant equations
ZR = R

3. The attempt at a solution
I'm not really sure about any of this. Across the resistor, the complex impredence is just R and so has no dependence on the angular frequency, but just plotting a stright line with amplitude IR can't be worth 5 marks (which is the marks for this question). Can someone explain this to me?

#### Attached Files:

• ###### circuit.png
File size:
858 bytes
Views:
97
2. Jun 10, 2010

### vela

Staff Emeritus
The current I varies with frequency.

3. Jun 11, 2010

### graphene

the L & C impedances vary with frequency.
So, the voltage across the resistor should also vary as it is in series with the L-C combination.

Find out the total impedance of the parallel combination of L & C (which is a function of w).
Now R is in series with this combo-impedance.