Question 1: A voltage pulse shown below is applied to a load and the current through the load was measured and is also shown.
(a) Find the RMS value of the voltage v(t).
(b) Find the RMS value of the current i(t).
(c) Find the average power developed across the load.
(d) Is the load best described as resistive, reactive, or mixed? Briefly Explain.
Question 2: A capacitive load is connected directly to an AC current source as shown.
(a) Draw a phasor diagram for the circuit, show all currents, voltages, and clearly indicate the axes.
(b) Explain, by means of a phasor diagram, how the cm-rent drawn from the source may be reduced by adding an inductor in parallel with the load. What should the impedance of this inductor be in order to minimise the current?
Question 3: Consider the circuit shown.
(a) Find the voltage across the capacitor.
(b) Find the Thevenin equivalent circuit seen from terminals a-b.
(c) If a variable resistor is to be connected to the terminals, what should its resistance be in order to receive maximum average power? Find the maximum average power that can be delivered to this resistor.
Question 4: A Load with all impedance of ZL = 6+ j8 Ω is connected to a sinusoidal supply of 240 VRMS.
(a) Calculate the complex power of the load.
(b) Calculate the power factor of the load.
(c) Explain why the current through the load can be increased by adding a capacitor in series with the load. What should the impedance of this capacitor be in order to allow maximum current through the load?
(d) With the inclusion of the capacitor in (4 calculate the maximum average power that can be absorbed by the load ZL.
Question 5: The magnitude of the phase voltage of an ideal balanced three-phase Y- connected source is 125 V(rms). The source is connected to a balanced Y-connected load by a distribution line that has an impedance of 0.1 + j14.2 Ω/Φ. The load impedance is 19.9 + j14.2 Ω/Φ. The phase sequence of the source is positive. Use the a-phase voltage of the source as the reference.
(a) Construct the single-phase equivalent circuit of the system using the a-phase.
(b) Calculate the three line currents through each of the distribution Lines.
(c) Calculate the three phase voltages at the load.
(d) Calculate the three line voltages at the load.