# Homework Help: RMS Current

1. Mar 13, 2006

### thenewbosco

Four circuit elements—a capacitor, an inductor, a resistor, and an AC source—are connected together in various ways.
First the capacitor is connected to the source, and the rms current is found to be 25.1 mA. The capacitor is disconnected and discharged, and then connected in series with the resistor and the source, making the rms current 15.7 mA. The circuit is disconnected and the capacitor discharged. The capacitor is then connected in series with the inductor and the source, making the rms current 68.2 mA. After the circuit is disconnected and the capacitor discharged, all four circuit elements are connected together in a series loop.
What is the rms current in the circuit?

i was thinking to use the following: $$I_{rms}=\frac{\Delta V_{rms}}{Z}$$ where Z is the impedance given by $$Z=\sqrt{R^2 + (X_L-X_C)^2$$, however i dont have the root mean square voltage...

any hints on how to approach this problem... thanks

2. Mar 14, 2006

### plusaf

just a shot in the dark... it's late here...
start with an assumption of a unity driving signal... one volt rms and one Hz. i'd bet that in the end the frequency and voltage drop out of the final solution.