NEET AIPMT SOLVED PAPER SCREENING 2006

  • question_answer
                    A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be:

    A)                                                                                                                                                                                             \[f/4\] 

    B)                  \[8f\]                   

    C)                  \[f/2\sqrt{2}\] 

    D)                 \[f/2\]

    Correct Answer: C

    Solution :

                    In a series LC circuit, frequency of LC oscillations is given by                 \[f=\frac{1}{2\pi \,\sqrt{LC}}\] \[orf\,\propto \,\,\frac{1}{\sqrt{LC}}\] \[\Rightarrow \frac{{{f}_{1}}}{{{f}_{2}}}=\sqrt{\frac{{{L}_{2}}{{C}_{2}}}{{{L}_{1}}{{C}_{1}}}}\] Given,   \[{{L}_{1}}=L,\,{{C}_{1}}=C,\,{{L}_{2}}=2L,\,{{C}_{2}}=4C,\,\,{{f}_{1}}=f\] \[\therefore \frac{f}{{{f}_{2}}}=\sqrt{\frac{2L\times 4C}{LC}}=\sqrt{8}\] \[\Rightarrow {{f}_{2}}=\frac{f}{2\sqrt{2}}\]


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