AdvancedA-001-005-005
What is the Q of a parallel RLC circuit, if it is resonant at 7.125 MHz, L is 8.2 microhenrys and R is 1 kilohm?
D
Answer
Advanced theory and components
Type
A
0.273
B
36.8
C
0.368
D
2.73
Answer Notes
The Q factor of a parallel RLC circuit is found by dividing the parallel resistance by the inductive reactance (Q = R / X_L). This relationship means that in a parallel circuit, a higher resistance leads to a higher Q, unlike in a series circuit.
First, find the inductive reactance (X_L) at the resonant frequency using the formula X_L = 2 * π * f * L. With f = 7.125 MHz and L = 8.2 µH, the megahertz and microhenrys cancel out their magnitude differences. X_L = 2 * 3.1416 * 7.125 * 8.2 ≈ 367.1 ohms.
Then, convert the resistance to ohms (1 kilohm = 1,000 ohms) and divide it by the reactance. Q = 1000 / 367.1 ≈ 2.73.
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What is the Q of a parallel RLC circuit, if it is resonant at 14.225 MHz, L is 3.5 microhenrys and R is 10 kilohms?
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What is the Q of a parallel RLC circuit, if it is resonant at 7.125 MHz, L is 10.1 microhenrys and R is 100 ohms?