A portable AM radio is to be tuned by adjusting only its capacitor while the…
PHYSICS · Multi-part · CBSE · Physics · Alternating Current · Alternating Current
Problem
A portable AM radio is to be tuned by adjusting only its capacitor while the inductance remains fixed. The receiver must cover the broadcast band from 530 kHz to 1 610 kHz.
(i) Write the expression for the resonant frequency of a series LCR circuit and identify the parameters on which it depends.
(ii) Using the expression obtained in (i), explain qualitatively how increasing the capacitance while keeping the inductance fixed affects the resonant frequency.
(iii) Give two practical reasons, based on circuit construction and component behaviour, why a variable capacitor is generally preferred over a variable inductor for tuning such radios.