Question

As the frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit?

Options

• Inductor and capacitor

• Resistor and inductor

• Resistor and capacitor

• Resistor, inductor and capacitor

Answer 1

Inductor and capacitor and Resistor, inductor and capacitor

Explanation:

Impedance is given by,

Z = \[\sqrt{R^2+\left(X_L-X_C\right)^2}=\sqrt{R^2+\left(2\pi fL-\frac{1}{2\pi fC}\right)^2}\]

At resonance frequency, Z is minimum and current is maximum. For any other value of frequency, the value of current will decrease (when compared to current at resonance).

Clearly circuit must have inductor and capacitor of equal reactance.