A 1 μ F capacitor has 2,652 Ω of reactance at 60 Hz. What is the reactance value at 400 Hz?

A) 397.88 Ω
B) 568.72 Ω
C) 639.79 Ω
D) 768.33 Ω

The reactance $X_C$ of a capacitor is given by $X_C=\frac{1}{2\pi fC}$ , where $f$ is the frequency and $C$ is the capacitance. Since reactance is inversely proportional to frequency, you can calculate the new reactance at 400 Hz by using the ratio of the frequencies. Given the reactance at 60 Hz is 2,652 Ω, the reactance at 400 Hz can be found as follows: $X_{C_{400Hz}}=X_{C_{60Hz}}\times \frac{60}{400}=2652\times \frac{60}{400}=397.8\Omega$ .