Electronics Engineering (ELEX) Board Practice Exam

If the source voltage is 20/_0° at 20 kHz and the circuit has specific values, what is the voltage across the inductor?

1. 15.0/_30° V_pp

2. 17.9/_25.3° V_pp

3. 20.0/_0° V_pp

4. 22.1/_15° V_pp

The correct answer is: 17.9/_25.3° V_pp

The voltage across the inductor in an AC circuit is influenced by the inductor's reactance, which can be calculated using the formula \( X_L = 2 \pi f L \), where \( f \) is the frequency and \( L \) is the inductance. As the frequency increases or the inductance value increases, the reactance also increases, resulting in a larger voltage drop across the inductor. In this scenario, with a source voltage of 20 V at an angle of 0 degrees, the inductive nature causes the voltage across the inductor to lead the current. The calculated voltage across the inductor, which is given as 17.9 V at an angle of 25.3 degrees, suggests that the circuit is operating under certain reactive conditions. This specific voltage can be derived from the application of Kirchhoff's voltage law and the impedance characteristics of the circuit, taking into account both the resistive and reactive components. The phase angle indicates how much the voltage across the inductor is leading compared to the source voltage. The calculated value matches the expected behavior of inductive circuits where the voltage across inductors tends to be higher than the source voltage due to their reactive nature. Thus, the voltage across