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4. (a) A resistor network is shown in Figure 4(a). By applying the Kirchhoff's (6 marks) current law, determine the value of the currents I1, 13 and 14. 14 11 13 Is=50A 17 = 100A 12=30A 16-20A Figure 4(a) (6) As shown in Figure 4(b), a series RLC circuit is connected to a 50 V 50 Hz AC supply. The circuit consists of a 20 s2 resistor, a 25 mH inductor, and a 200 uF capacitor. (1) Determine the total impedance (Z) in rectangular form. (3 marks) (ü) Calculate the supply current (1) in polar form; and (2 marks) (iii) Calculate the voltages across the resistor (Vr), inductor (VL), and capacitor (3 marks) (Vc) in polar form (iv) Sketch a phasor diagram to show the supply current (I), supply voltage (V), (5 marks) and voltages across the resistor (Vr), inductor (VL), and capacitor (Vc). 50 V, 50 Hz R L с m Figure 4(6) (©) A student is doing a test for the LRC circuit similar with connection shown (6 marks) in Figure 4(6). He takes a resistor with a low resistance value. Then, he randomly picks an inductor and capacitor. At last, he connects a 220 V a.c. to all of them in series. However, it is found that the protection fuse of the circuit is blown. Identify the possible problem with explanation