The reactance of a 4.00 μF capacitor at 80 Hz is
1 / (2 · π · f · C) =
1 / (2 · π · 80 · 4 x 10⁻⁶) =
- 497.4 ohms .
Before I can work out the impedance of the circuit, I have to know the resistance, inductance, and capacitance in the circuit, and how they're all configured ... series, parallel, some of both, etc. Also the frequency at which the circuit is operating.