How can you change the resonant frequency of a circuit?

How can you change the resonant frequency of a circuit?

• A. By changing its resistance
• B. By changing its capacitance or inductance
• C. By altering the supply voltage
• D. By changing the physical layout of the circuit

Answer: (B)

The resonant frequency of a circuit is set by how quickly energy can swap between the magnetic field of the inductor and the electric field of the capacitor. In an LC circuit, the natural frequency is given by f0 = 1/(2π√(LC)). So changing either the inductance or the capacitance directly changes the rate of that energy exchange: increasing L or C lowers the frequency, while decreasing them raises the frequency. Resistance mainly affects how sharply the resonance is defined (damping) and not the center frequency in an ideal case; the supply voltage influences how large the oscillations are but not how fast they occur. Changing the physical layout can alter stray inductances or capacitances and thus can shift f0 somewhat, but the direct way to control the resonant frequency is by adjusting the inductance or capacitance.

The resonant frequency of a circuit is set by how quickly energy can swap between the magnetic field of the inductor and the electric field of the capacitor. In an LC circuit, the natural frequency is given by f0 = 1/(2π√(LC)). So changing either the inductance or the capacitance directly changes the rate of that energy exchange: increasing L or C lowers the frequency, while decreasing them raises the frequency. Resistance mainly affects how sharply the resonance is defined (damping) and not the center frequency in an ideal case; the supply voltage influences how large the oscillations are but not how fast they occur. Changing the physical layout can alter stray inductances or capacitances and thus can shift f0 somewhat, but the direct way to control the resonant frequency is by adjusting the inductance or capacitance.