When tuning a radio receiver, how do you change the resonance of the circuit?

When tuning a radio receiver, how do you change the resonance of the circuit?

• A. By increasing the coil current
• B. By changing the supply frequency
• C. By altering the resistor value
• D. By moving plates of the capacitor

Answer: (D)

Resonance in a radio tuner comes from an LC circuit, and the frequency at which it resonates depends on both the inductance L and the capacitance C, following f = 1/(2π√(LC)). To change which frequency the circuit resonates at, you modify the capacitance. A variable capacitor does this by moving its plates, changing how much charge the plates can store (altering C). When you adjust the plate spacing or overlap, you shift the resonant frequency and thus select a different station. Increasing coil current wouldn’t change the resonance point; it mainly affects signal strength. Changing the supply frequency isn’t how you tune the front end, and changing a resistor mostly affects the sharpness of the resonance, not its position. Moving the plates of the capacitor is the mechanism that shifts the resonance.

Resonance in a radio tuner comes from an LC circuit, and the frequency at which it resonates depends on both the inductance L and the capacitance C, following f = 1/(2π√(LC)). To change which frequency the circuit resonates at, you modify the capacitance. A variable capacitor does this by moving its plates, changing how much charge the plates can store (altering C). When you adjust the plate spacing or overlap, you shift the resonant frequency and thus select a different station. Increasing coil current wouldn’t change the resonance point; it mainly affects signal strength. Changing the supply frequency isn’t how you tune the front end, and changing a resistor mostly affects the sharpness of the resonance, not its position. Moving the plates of the capacitor is the mechanism that shifts the resonance.