AdvancedA-001-003-004

What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 25 microhenrys and C is 10 picofarads?

B
Answer
Advanced theory and components
Type
A
63.7 MHz
B
10.1 MHz
C
10.1 kHz
D
63.7 kHz

Answer Notes

The formula for determining resonant frequency is f = 1 / (2π√(LC)). As with all ideal series RLC circuits, the resistor value (47 ohms) determines the bandwidth but does not shift the center resonant frequency. Using the provided values of L = 25 × 10^-6 H and C = 10 × 10^-12 F, we first multiply them to get 2.5 × 10^-16. Taking the square root gives about 1.581 × 10^-8, and multiplying by 2π results in 9.934 × 10^-8. Taking the reciprocal (1 / x) of this denominator yields exactly 10,066,000 Hz, or 10.1 MHz. Distractors involving 63.7 or values in kHz stem from either dropping the 2π from the formula or mismanaging scientific notation.
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What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 50 microhenrys and C is 10 picofarads?
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What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 3 microhenrys and C is 40 picofarads?