Electronics Engineering (ELEX) Board Practice Exam

What is the impedance of the network at a frequency of 10 kHz?

1. 162.6/_-84.8°

2. 160/_-90°

3. 170/_-80°

4. 150/_-75°

The correct answer is: 162.6/_-84.8°

The impedance of an AC network at a specific frequency depends on the values and types of components present in the circuit, such as resistors, capacitors, and inductors. In this instance, the correct answer provides an impedance value of 162.6 ohms at an angle of -84.8 degrees, which indicates that the network is primarily capacitive. The magnitude of this impedance, 162.6 ohms, suggests a significant reaction to the AC signal, while the phase angle of -84.8 degrees implies that the current leads the voltage in the circuit, which is characteristic of capacitive behavior. In capacitive circuits, the impedance decreases as the frequency of the AC signal increases, a relationship that is reflected in the resulting phase angle. In contrast, the other options present impedance values and phase angles that either do not correspond to the expected behavior of the network at 10 kHz or suggest different component contributions that are less consistent with a high-frequency response typical of capacitor-dominated networks. The given impedance value and angle indicate a circuit where capacitive reactance predominates, making the first option the most accurate representation of the network's impedance at that frequency.