45 and 47

​Q45. In a series LCR circuit, the inductive reactance is twice the resistance and the capacitive reactance is the inductive reactance. The power factor of the circuit is 

   (1) 0.5                       (2) 0.6                     (3) 0.8                      (4) 1


Q47. A radio tuner has a frequency range from 500 KHz to 5 MHz. If its LC circuit has an effective inductance of 400 $\mathrm{\mu }$H, the range of its variable capacitor is (Take ${\mathrm{\pi }}^2$ = 10) 

     (1) 250 pF to 2.5 pF            (2) 500 pF to 5500 pF          (3) 7.5 pF to 750 pF              (4) 1000 pF to 10 pF