Question 2
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(a) Explain the term resonance in a series RLC circuit.
(b) Figure 2 is a series RLC circuit.
Figure 2If the impedance of the circuit is 120 Ω at a frequency of 65 Hz, calculate the:
- inductive reactance;
- capacitance of the capacitor.
Observation
The expected responses were:
(a) Resonance occurs when the inductive and capacitive reactance are equal in magnitude.
(b) (i) XL = 2π f L
= 2π × 65 × 30 × 10-3
= 12.25 Ω
(ii) XC = 
Since Z = 120 Ω = R
Then, | XC | = | XL |
XC = 12.25 Ω
12.25 = 
C = 
= 199.9 x 10-6 F
C = 0.0002 F = 200