In an LC oscillator, if values of inductance and capacitance become twice and eight times, respectively, then the resonant frequency of oscillator becomes times its initial resonant frequency . The value of is:
- A
- B
- C
- D
In an LC oscillator, if values of inductance and capacitance become twice and eight times, respectively, then the resonant frequency of oscillator becomes times its initial resonant frequency . The value of is:
Correct answer:A
Standard Method
Given: In an LC oscillator, inductance becomes and capacitance becomes .
Find: The factor such that the new resonant frequency is .
The resonant frequency of an LC circuit is given by
When and , the new resonant frequency is
Thus, the value of is . The correct option is A.
The resonant frequency of an LC oscillator decreases as the inductance and capacitance increase, since .
Using direct proportionality with instead of inverse square-root dependence is incorrect. The resonant frequency varies as , so increasing and decreases the frequency. Always apply the square root in the denominator.
Multiplying the change factors incorrectly is a common error. Here, becomes and becomes , so the product becomes , not . First combine the scaling factors correctly, then take the square root.
Forgetting to compare the new frequency with the initial frequency leads to confusion about . The question asks for the multiplicative factor relative to , so rewrite the new result as a multiple of before choosing the option.
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