question_answer 10)

A radio can tune over the frequency range of a portion of MW broadcast band: (800 kHz to 1200 kHZ). If its LC circuit has an effective inductance of what must be the range of its variable capacitor?                 [Hint. For tuning, the natural frequency i.e., the frequency of' free oscillations for the LC circuit should be equal to the frequency of the radiowave.]  

Answer:

                Using we get                 i.e.,                                 Similarly for 1200 kHZ, we get                                 = 87.9 pF.                 Thus the range of variable capacitor must be 88 pF to 198 pF.