Problem 58-6    Source:   Example 14.5 - page 317 - HUGGES, A. E. - Book: Electrical and Eletronic Technology - 10ª ed. - Editora Pearson - 2008.

A coil of 1 kΩ resistance and 0.15 H inductance is connected in parallel with a variable capacitor across a 2.0 VAC, 10 kHz supply as shown in Figure 58-06.1. Calculate:

a) the capacitance of the capacitor when the supply current is a minimum;

b) the dynamic impedance, Z_d, of the network at resonance;

c) the supply current.

Solution of the Problem 58-6   

Item a

When the circuit is in resonance, the current consumed is minimal. Using eq.58-4 and working algebraically, we get:

Substituting the numerical values ​​and performing the calculation:

Item b

To find the dynamic impedance, we use eq. 58-19, reproduced below.

Substituting the respective numerical values, we have:

Item c

And, of course, the current supplied by the voltage source is given by: