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Question 1 [20 marks] a) Briefly explain Kirchhoff's current and voltage laws using circuit diagrams and equations to support your answer. [4 marks] b) Explain the advantages of 3-phase system over the single-phase system. [2 marks] c) State at least two characteristics of an ideal operational amplifier. [2 marks] d) A lightning bolt carried a current of 3 kA and lasted for 2 ms. How many coulombs of charge were contained in the lightning bolt? [2 marks] e) [2 marks] Determine the resistance of an electric heater that draws 15 A from a 240 V line. f) Determine the current i, in Figure 1. [2 marks] g) Find V, in the circuit shown in Figure 2. 192 www 15 V 6A Figure 1 2 V, 502 wwwww 292 Figure 2 h) Show the circuit diagram for the boolean expression Y = AB + CD [3 marks] [3 marks] Question 2 [15 marks] a) The power rating of the appliances and average duration for which they are used in a day for a domestic household are given in Table 1. Calculate the electricity bill for the month of November if the cost of electricity is 34.01 cents per kWh and VAT is charged at a rate of 9%. [6 marks] Please Turn Over EEB501 - Introduction to Electrical & Electronics Engineering Semester 2, 2021 Table 1 Appliance Rating 60W TV Laptop 40W Mobile Charger 2W Electric Heater 1500W Usage SOVO 90 V 4 hours 5 hours 5 hours Freezer 24 minutes Washing Machine Appliance Light 1 Light 2 60 F HH 30 F Figure 3 Rating 20 F HH 14 F 40W 80W 50W 320W b) Analyze the circuit given in Figure 3 and determine the total equivalent capacitance, and the voltage drop across the 20F capacitor. [9 marks] Page 2 of 5 80 F Usage 10 hours 6 hours. 24 hours 30 minutes Question 3 [25 marks] a) Apply source transformation to find v, in the circuit shown in Figure 4. 50 V 102 www 3 A a 1292 b www. + 40 2 Figure 4 b) Apply Thevenin's theorem to find v, in the circuit of Figure 5. 402 wwww 162 592 2012 www 8 A Figure 5 Please Turn Over 19 www 12 V 10 42 40 V [10 marks] [10 marks] c) The switch in the circuit given in Figure 6 has been closed for a long time and is opened at t = 0. Find the current through the 4 k2 resistor for t > 0. [5 marks] 6 V 2 km2 www % 1=0 Figure 6 4kQ 3 mF Question 5 [20 marks] a) Determine the power factor of the circuit and the current flowing through the capacitor in the circuit given in Figure 9. [10 marks] 2/30 A 392 j402 www.m 592 -j2Q 652 Figure 9 b) A delta-connected source supplies power to a delta-connected load in a balanced three-phase system. Given that the line impedance is 2 + j1 per phase while the load impedance is 6 + j4 per phase, find the voltage across the load. Assume a positive sequence with the source phase voltage Vab= 208 20 Vrms- [10 marks]