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August StudentZone Quiz Solution

Question 1:

Calculate the value of the parasitic capacitance.

Answer 1:

We consider the measured value of period for the self-resonance waveform with a 4.7mH inductor.

The approximate value for the measured period is 0.1mS.

Using the formula of the resonant frequency:


We obtain


The resulting parasitic capacitance of the inductor is:

C = 54nF


Question 2:

Inductors also have an internal series resistance that should not be ignored when they are modeled. What aspect of the oscillating signal you measured for the LC circuit is caused by the resistance?

Answer 2

The internal series resistance, even if it has a small value, it represents a discharging path for LC components that hold charges. It is responsible of the damping oscillation of the circuit.