Electro Magnetic Induction And Alternating Currents Question 221

Question: 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

Options:

A) $ 8f $

B) $ f/2\sqrt{2} $

C) $ f/2 $

D) $ f/4 $

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Answer:

Correct Answer: B

Solution:

  • We know that frequency of electrical oscillation in L.C. circuit is

$ f=\frac{1}{2\pi }\sqrt{\frac{1}{LC}} $

Now, L=2L & C=4C $ f’=\frac{1}{2\pi }\sqrt{\frac{1}{2L\cdot 4C}}=\frac{1}{2\pi }\sqrt{\frac{1}{LC}}\times \frac{1}{2\sqrt{2}}\Rightarrow ,f’ $

$ =\frac{1}{2\sqrt{2}}\times f $



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