An ac circuit has a 100-Ω resistor in series with a 4.9-μF capacitor and a 700-mH inductor.At what frequency does the circuit act like a pure resistance?
A)0.29 MHz
B)1.9 MHz
C)12 MHz
D)0.54 kHz
E)86 Hz

Question

Quizplus · Accepted Answer

The circuit acts like a pure resistance at its resonant frequency, where the inductive reactance equals the capacitive reactance. The resonant frequency is given by f = 1/(2π√(LC)), where L is the inductance and C is the capacitance. Substituting L = 700 mH and C = 4.9 μF gives approximately 86 Hz.

An Ac Circuit Has a 100-Ω Resistor in Series with a 4.9-μF